Instrument test questions

III. Multiple-choice Questions 1. In which of the following situations does ( ) constitute a systematic error? A. Errors caused by miscalculated numbers ； B. Errors caused by recording mistakes ； C. Errors caused by incorrect installation ； D. Errors caused by misreading the scale. 2. The accuracy class of a meter refers to the ( ) of the meter. A. Error ； B. Basic error ； C. Maximum error ； D. Allowable error ； E. Basic error and maximum allowable value 3. The accuracy of an instrument is related to ( ). A. Relative error ； B. Absolute error ； C. Measurement range ； D Basic error 4. The error that we cannot control is ( ). A. Negligence error ； D, slowly varying error ； C. Random error ； D System error 5. The error caused by the aging of internal components of the instrument is called ( ). A. Negligence error ； B. Slowly varying error ； C. Random error ； D. Systematic error 6. Differential pressure transmitters with diaphragm structures typically measure differential pressures that are much lower than the operating pressure. Due to operational or other factors, it is inevitable that the diaphragm will be subjected to pressure in one direction; in order to prevent the measuring element from being affected by this, such structures include ( ). A. Limiting device ； B. Locking device ； C. Pressure relief device ； D. One-way overload protection device 7. When flushing the differential pressure measurement pipeline, ( ) should be opened first. A. Secondary valve ； B. Waste discharge valve ； C. Balance valve ； D. Single-valve 8. For a vernier caliper with an accuracy of 1/20, the difference between each scale mark on the main scale and those on the vernier scale is ( ). A. 0.5mm ； B. 0.1mm ； C．O.05mm ； D. O.Olmm 9. When terminal blocks are installed side by side, the spacing between them should not be less than ( ) mm. A. 50 ； B. 100 ； C. 150 ； D. 1200 10. Under a step increase in steam flow rate, the drum water level ( ). A. exhibits a \"false water level\"” ； B. Rise immediately ； C drops immediately ； D. Unchanged 11. The temperature measurement range of a copper thermoresistor is ( ). A. O～500℃ ； B. -200~850℃ ； C. 0~1000℃ ； D. -50~150℃ 12. The positive terminal of the KX extended thermocouple compensation wire is red, and the negative terminal is ( ). A. Green ； B. Black ； C. Purple ； D. White 1.A, B, D 2.E 3.B, C 4.C 5.B 6.A 7.C 8.C 9.C 10.A 11.B 12.B 13.The equilibrium temperature between ice and saturated water in air is called ( ). A. Boiling point ； B. Freezing point ； C. Triple point ； D. Freezing point 14. Among the following thermocouples, the one with the greatest electromotive force and highest sensitivity is the ( ) type thermocouple. A.K ； B. S ； C. E ； D．J 15. The absolute zero is ( )°C. A. -273.16 ； B.-273.15 ； C．273．16 D．O 16. When the temperature sensing element is installed at an angle to the process pipeline, it should be inserted ( ) the flow direction of the medium. A. Along ； B. Against the flow ； C is not subject to the above regulations. 17. The model of the bimetallic thermometer is ( ). A. WNG ； B. WNY ； C. WSS ； D．WTZ 18. The maximum operating indication value of a temperature instrument is generally ( ) of the full scale. A．90％ ； B. 100% ； C. 50% ； D. 80% 19. The finer the even yarn, then ( ). A. The higher the sensitivity ； B. The faster the reaction ； C. The more durable it is ； D. The lower the sensitivity, 20. The installation of pressure gauges on-site requires ( ). A. Vertical ； B. Inclination ； C. Horizontal ； D. Any angle 21. Changes in atmospheric pressure have an impact on calibrating absolute pressure transmitters ( ). A. Yes ； B. None 22. When a torsion tube float level gauge is used to measure the liquid level, the higher the liquid level, the greater the torsional angle generated by the torsion tube ( ). A. The larger ； B. The smaller ； C. Unchanged ； D. Not necessarily. 23. Which of the following materials has the strongest shielding effect against gamma rays? ( ) A. Iron ； B. Lead ； C. Concrete ； D. Aluminum 13.D 14.C 15.A 16.B 17.C 18.A 19.B 20.A 21.A 22.B 23.B 24. Which of the following belong to variable buoyancy type level gauges? ( ) A. Float level gauge ； B. Lever-type floating level gauge ； C. Float level gauge ； D. Flip-type level gauge 25. The correct statement regarding the proportionality and integration time of a regulator is ( ). A. The greater the proportionality, the stronger the proportional action ； B. The smaller the integration time, the stronger the integrating effect ； c. The greater the gain, the weaker the proportional action; the greater the integration time, the stronger the integral action ； D. The smaller the proportionality, the weaker the proportional action; the smaller the integration time, the weaker the integral action. 26. The principles that should be followed in selecting the parameter to be regulated are ( ). A. Can represent process operation parameters or reflect the status of process operations ； B. Measurable and with sufficient sensitivity ； C. Independent and controllable ； D. Try to use direct indicators whenever possible ； E. Engineering units must be used. 27. A multi-stage control system generally has ( ) control valves. A. 1 ； B. 2 ； C. 3 ； D. 4 28. In a cascade control system, the secondary controller usually adopts a ( ) control law. A. PI ； B. PID ； C. PD ； D. P 29. Functionally, a pneumatic valve positioner generally consists of components such as the input ( ). A. Compare, zoom in ； B. Comparison, amplification, feedback ； C. Comparison, amplification, feedback, and control mechanisms 30. There is an electrical valve positioner that receives an input current signal, but the actuator does not move. What do you think are the possible reasons? ( ) A. The torque conversion coil is broken ； B. The supply pressure does not meet the requirements ； C. Connection error 31. The nominal diameter of a steel pipe usually refers to the ( ) of the steel pipe. A. Outer diameter ； B. Inner diameter ； C. None of them. 32. Which of the following has requirements regarding the flow direction of pneumatic control valves during installation? A. Butterfly valves, ball valves, diaphragm valves ； B. Single-seat valve, double-seat valve, three-way valve, sleeve valve ； C. Angle valves, high-pressure valves, eccentric rotary valves ； D. Self-acting control valve 24.C 25.B 26.A, B, C, D 27.B 28.C 29.B 30.B, C 31.C 32.B, C, D 33. The optimal location for installing a straight-stroke control valve on a process pipeline is ( ). A. Horizontal ； B. Vertical ； C. Arbitrary 34. The DCS system is also known as ( ). A. Centralized control system B. Distributed control system C. Computer-controlled system D. Distributed control and monitoring system 35. The abbreviation for a programmable controller is ( ). A. DCS ； B. BMS ； C. CRT ； D. PLC 36. The maximum operating indication value for temperature instruments is generally ( ) of the full scale. A. 90% ； B. 100% ； C. 50% ； D. 80% 37. The local thermometer with high accuracy is ( ). A. Pressure-type thermometer ； B. Glass liquid thermometer ； C. Bimetallic thermometer 38. In a pneumatic pressure transmitter, as the output increases, the distance between the nozzle and the baffle ( ). A. Increase ； B. Unchanged ； c. Reduce 39. Possible reasons why the pointer of a pressure gauge does not return to zero after the pressure is removed are ( ). A. The pointer is bent ； B. Insufficient hairspring torque ； C. Loose pointer ； D. Friction exists in the drive gears. 40. When using a float level gauge to measure the level of a fluid with a density lower than that of water, and when calibrating the range points of this float level gauge using water, the water fill height should be ( ) greater than the length of the float. A. High ； B. Low ； C. Equal ； D. Unclear 41. The gap at the joints between adjacent panels, cabinets, or tables shall not be greater than ( ). A, 2mm ； B, 1 mm ； C、1.5 mm 42. The rotameter should be installed on a pipe free from vibrations, and the angle between its centerline and the vertical line should not exceed ( ). A, 30º ； B, 20º ； C, 40º 33.B 34.B, D 35.D 36.A 37.B 38.C 39.A, B, C, D 40.B 41. A 42. B 43. The signal wires of turbine flowmeters should be shielded; the lengths of the straight sections upstream and downstream must meet the requirements specified in the design documents. The distance between the pre-amplifier and the transmitter should not exceed ( ). A、 5m ； B, 3 m ； C. 4 m 44. The shielding layer of the instrument cable shall be grounded on the ( ) side. A. Control room instrument panel cabinet ； B. On-site instrumentation equipment 45. When using an isolator filled with isolation fluid for isolation, the isolation container should be installed （ ）。 A. Horizontal ； B、Vertical: 46. When welding pipes of different diameters together, the difference in their inner diameters should not exceed ( ) mm; otherwise, reducers should be used. A、0.5 ； B, 1 ； C, 2 ； D、3 47. The spacing between pipeline supports should be uniform; when seamless steel pipes are laid horizontally, the distance between the supports is ( ) m. A、0.8～1 ； B, 1～1.5 ； C, 1.5～2 ； D、2～2.5 48. When seamless steel pipes are installed vertically, the distance between supports is ( ) m. A, 1～1.5 ； B, 1.5～2 ； C, 2–2.5 ； D、2.5～3 49. Before installation, the ports of the pipes should be temporarily sealed to avoid ( ). A. Damaged pipe end ； B、Rusting ； C. Entry of stolen goods ； D. Deformation 50. Which of the following is not a throttling device? A. Orifice plate ； B. Nozzle ； C. Long-diameter nozzle D. Anemometer tube 51. When making connections, a maximum of ( ) wires are allowed per terminal. A, 1 ； B, 2 ； C, 3 ； D、4 52. When the medium being measured is corrosive, it is necessary to install a ( ) in front of the pressure gauge. A、Isolation device ； B. Cooling device ； C. Buffering device ； D. Balancing device 53. The safety production policy is ( ). A. Safety must be taken into account in production management ； B. Safety in production is everyone’s responsibility ； C. Safety first, prevention foremost ； D. Implementing the safety production responsibility system 54. When insulated wires are used for low-voltage overhead lines, the overhead height shall not be lower than ( ). A, 3m ； B, 2.5m ； C、5 D、3.5m 55. For plastic pipes, the bending radius should not be less than （） of their outer diameter. A、3.5 ； B, 4.5 ； C, 5 ； D. 6 56. The grinding wheel of a grinder must be replaced when its effective radius is worn down to ( ) of its original radius. A, 1/2 ； B, 1/3 ； C, 2/3 ； D, 1/4 43. B 44. A 45. B 46. C 47. B 48. B 49. C 50. D 51. B 52. A 53. C 54. B 55. B 56. B 57. When the human body is exposed to radiation, ( ) A. one will definitely get sick ； B. It does not affect health within the allowable dose range. 58. When measuring the liquid in process equipment where stopping is not allowed easily, ( ) should be selected. A. Internal float level gauge ； B. External float level gauge 59. If the polarity of the compensation wire is reversed in the wiring, the instrument’s indication will ( ). A、Too large ； B、Too small ； C. It could be large or small, depending on the specific circumstances. 60. The error caused by changes in static pressure on a differential pressure transmitter is ( ). A. Random error ； B. Systematic error ； C. Negligible error 61. The accuracy class of a gauge refers to the ( ) of the gauge. A. Allowable error ； B. Basic error ； C. Maximum error ； D. The maximum allowable value of the basic error is 62. Pipe threads that can be sealed with threads are ( ). A. Ordinary pipe threads ； B、Cylindrical pipe thread ； C. Tapered pipe threads 63. When installing pressure tapping components on horizontal and inclined pipes, the location of the point from which liquid pressure is measured should be ( ) A. In the upper half of the pipe ； B. In the lower half of the pipeline, within an angle range of 0–45° relative to the horizontal centerline of the pipeline, 64. For the installation of instrument boxes, insulation boxes, and protection boxes, the allowable deviation in levelness is ( ) mm. A.3 ； B.4 ； C.2 65. For the installation of individual dashboards, cabinets, and control panels, the allowable deviation in verticality is ( ) mm/m. A.1 ； B.1.5 ； C.2 66. The ambient temperature during the installation of rubber-insulated cables should not be lower than ( ) °C. A.10 ； B.15 ； C.12 67. Which of the following expressions is correct? ( ) A. p_abs = p_surface + p_large ； B. p_table = p_absolute - p_max ； C. p-table = p-abs + p-large ； D. p_abs = p_table – p_large ； 57. B58. B59. C 60. B 61. D 62. C 63. B 64. A 65. B 66. B 67. A, B 1. The pressure of the heating steam generally does not exceed ( ) MPa. A.O. 5MPa ； B.1. 0MPa ； C. 1.5MPa ； D. 2.0 MPa 2. The instrumentation equipment is powered by a 24VDC supply, and its voltage range shall not exceed ( ). A. Soil 1% ； B. Soil 3% ； C. Soil 5% ； D. Soil 10% 3. There are many ways to resist interference, and twisted pair is one of those methods. A. Physical isolation ； B. Reduce magnetic interference ； C. Shielding ； D. Demagnetization 4. Atmospheric pressure decreases as altitude increases ( ). A. Increases ； B. Decrease ； C. Unchanged 5. The absolute error of the standard gauge used for calibrating pressure gauges should be less than ( ) of the absolute error of the gauge being calibrated. A. 1/2 ； B. 1/3 ； C. 1/4 ； D. 2/3 6. A pressure gauge used to measure the steam pressure in a pipeline is installed 5 meters below the pipeline; the pressure value it indicates is ( ) compared to the actual pressure inside the pipeline. A. higher ； B. Too small ； C. Unchanged 7. The higher the liquid level measured by a float-type level gauge, the greater the buoyant force acting on the float ( ). A. Greater ； B. The smaller, the better ； C. Unchanged ； D. Not necessarily. 8. Which of the following statements is incorrect? ( ) A. The regulator is the core component of a control system ； B. The regulator performs PID calculations based on the deviation between the set value and the measured value ； C. The regulator is equipped with automatic and manual control functions ； D. The digital regulator can receive 4–20mA current input signals. 9. It is generally believed that the dynamic process comes to an end after ( ) time. A. 3T ； B.T ； C. 5T ； D. 10T 10. The most detrimental type of disturbance for a control system is ( ). A. Step disturbance ； B. Sharp pulse interference ； C. Wide-pulse interference ； D. Random disturbances 11. ( ) has pure lag, but it does not affect the quality of regulation. A. Regulation channel ； B. Measurement element ； C transmitter ； D Interference channel 12. In a split-range control system, the segmentation of the signal ranges for the two valves is achieved by ( ). A. The regulator ； B. Electrical converter ； C. Valve positioner ； D. Transmitter 13. When a control valve operates at a low opening degree frequently, it is advisable to choose a ( ) characteristic. A. Equal percentage ； B. Quick open ； c Straight line 1.B 2.C 3.B 4.B 5.B 6.A 7.C 8.D 9.A 10.B 11.D 12.C 13.A 14. Which control valve is most suitable for controlling fluids with high viscosity, fibers, and fine particles? ( ) A. Butterfly valve ； B. Sleeve valve ； C. Angular valve ； D. Eccentric rotary valve 15. The basic circuit that constitutes a counter is ( ). A. NAND gate ； D. NAND gate ； C. OR gate ； D. Flip-flops 16. For the grounding system of a PLC, its grounding resistance should be less than ( ). A. 4Ω ； B. 6Ω ； C 7Ω ； D. 1Ω 17. The length of the straight sections upstream and downstream of the ultrasonic flow meter shall meet the requirements specified in the design documents. For horizontal pipes, the transducer should be positioned within an angle of ( ) degrees from the horizontal diameter. A、90º ； B, 30º ； C. 45º 18. The bending radius of the protective tube shall not be less than ( ) of the outer diameter of the protective tube. A, 5 times ； B, 6 times ； C, 7 times. 19. When measuring pipelines and connecting them to high-temperature equipment, what ( ) measures should be taken? A. Thermal expansion compensation ； B. Isolation ； C. Buffering 20. Oil pressure pipes should not be laid parallel above high-temperature equipment and pipes. The distance from the heat-surface insulation layer should be greater than ( ). A、100 mm ； B, 150 mm ； C, 200 mm ； D、250 mm 21. Carbon tetrachloride for industrial use, suitable for ( ) degreasing. A. Ferrous metals, copper, and non-metallic parts ； B、Metal parts ； C. Ferrous and non-ferrous metals 22. The bending angle of the wire conduit should not be less than ( ). A、90º ； B, 115º ； C, 130º ； D、120º 23. The pressure guide tube should be laid along the shortest possible path, and this is to ( ). A. Reduce heat loss ； B. Reduce vibration ； C. Reduce measurement latency ； D. Increase stability. 24. The distance between two adjacent source components should be greater than the outer diameter of the pipeline, but it must not be less than ( ) mm. A. 200 ； B300 ； C400 ； D500 25. All alloy steel components shall undergo ( ) before installation. A. Heat treatment ； B. Electroplating ； C. Material analysis ； D. Spectral analysis 26. When using a grinder, one should stand on the ( ) side of the grinder. A. Front side ； B、Side ； C、Between the two grinding wheels ； D, Back side: 14.B, 15.D, 16.A, 17.C, 18.B, 19.A, 20.B, 21.A, 22.A, 23.C, 24.A, 25.D, 26.B. Quality management is an important part of an organization’s ( ) activities. A. Functional management ； B. Professional management ； C. Comprehensive management ； D. Economic Management 28. The distance between an acetylene cylinder and open flames must be no less than ( ). A、5 meters ； B, 7 meters, C, 10 meters ； D、15 meters 29. The temperature-sensing element of a bimetallic thermometer must be ( ) when measuring temperature. A、1/2 submerged in liquid ； B. All extracts ； C、Impregnation 3/4 ； D. Submersion to any length. 30.G3/4″ refers to pipe threads, where 3/4″ denotes ( ). A. The inner diameter of the pipe ； B. Diameter of the threaded portion ； C. Wall thickness of the pipe ； D. Thread pitch 31. When drilling holes using a drill or impact drill, the drill bit should be placed against the work surface before starting to drill, in order to ( ). A. Avoid hitting empty spaces ； B. Increase speed ； C. Prevent deviation ； D. Shock absorption 32. The strength of cooled steel ( ) A. Decreases ； B. Increase ； C、Unchanged ； D. Becoming brittle 33. The welding position in which good weld formation is easy to achieve is ( ) A. Horizontal welding position ； B、Vertical welding position ； C. Upward welding position ； D. Flat welding position 34. A fixed pulley can ( ) A. save effort ； B. Save effort ； C. Change the direction of the force ； D. It saves both effort and time. 35. The basic properties of metal materials include their performance in use and ( ). A. Chemical properties ； B. Physical properties ； C. Mechanical properties ； D. Process performance 36. Failure to meet requirements means not satisfying ( ). A. Standards, regulations ； B. Product quality, quality system ； C. Explicit, usually implied, or necessarily fulfilled needs or expectations ； D. Standards, Contracts 37. The correct installation of the compensation wire should start from the thermocouple and extend up to ( ). A. On-site junction box ； B、Dashboard terminal board ； C. Secondary instruments ； D. The location at the same temperature as the cold-end temperature compensation device 27. C 28. C 29. B 30. A 31. A 32. B 33. D 34. C 35. D 36. C 37. D 38. For XWB and XWC instruments, it is specified that the resistance of the external signal wires shall not exceed ( ) A. 15Ω ； B, 1KΩ ； C、1.5 KΩ 39. The recorder can simultaneously record up to ( ) types of parameters. A、3 ； B, 6 ； C、12 40. The R value of the direct-acting single-seat control valve produced in our country is ( ). A、15 ； B, 30 ； C, 40 41. The 1151 differential pressure transmitters with different measurement ranges differ in terms of the ( ) of their measuring diaphragms. A、thickness ； B. Different materials ； C. Different diameters. 42. The measurement ranges of lever-type differential pressure transmitters vary mainly due to the ( ) of their measuring diaphragms. A. Different thicknesses ； B. Different materials ； C. Different diameters. 43. When using an electronic potentiometer to measure the temperature of a thermocouple, if the temperature at the hot end rises by 2°C, the room temperature (the temperature at the cold end) drops by 2°C; then the instrument’s reading ( ) A. Rises by 2℃ ； B, decrease by 2℃ ； C、Unchanged ； D. Increase by 4°C. 44. The outlet pressure of the oxygen compressor is around 25 MPa. Which of the following pressure gauges is suitable for measuring this value? ( ) A. A regular pressure gauge with a range of 0–25 MPa ； B. Pressure gauge for oxygen at 0~25 MPa C. Pressure gauge for oxygen at 0~40 MPa ； D. Oxygen pressure gauge for 0~60 MPa. 45. Once the instrument system has been in operation continuously for ( ) hours without any issues, it is then ready for handover and acceptance. A, 48 ； B, 24 ； C, 72 38. B39. C40. B 41. A42. C 43.A 44.D 45. A 1. The pressure and temperature corrections made in flow compensation are used to correct ( ) errors. A. Systematic errors ； B. Random error ； C. Negligence error ； D. Additional error 2. If a 1151 pressure transmitter has a grounding issue in its wiring, then ( ). A. The voltage will decrease ； B. Voltage increase ； c. Current decreases ； D. The current increases. 3. When measuring a stable pressure, the maximum operating pressure of the medium being measured shall not exceed ( ) of the instrument’s range. A. 1/2 ； B. 1/3 ； C. 2/3 ； D. 3/5 4. A 1151 pressure transducer has a measurement range of 0–300 kPa. If the zero point shifts upward by 50%, then the instrument’s actual measurement range will be ( ). A. 150kPa ； B. 300kPa ； C 450kPa ； D. 250kPa 5. If it is found that the range of a pressure transmitter is too small when it is in use on-site, and the transmitter’s range is increased while the range of the secondary display instrument remains unchanged, then the measured pressure value will be ( ) compared to the actual pressure value. A. higher ； B. Too small ； C. Unchanged 6. In the quality indicators of transition processes, the residual error represents ( ). A. The difference between the new stable value and the given value ； B. Difference between measured value and given value ； C. Adjust the difference between the parameter being adjusted and the reference parameter ； D. The difference between the overshoot and the set value. 7. Regarding the block diagram of a control system, which statement is correct? ( ) A. A square represents a device ； B. The lines connecting the squares represent the material relationships between them ； c. The lines connecting the squares represent the energy relationships between them ； D. The lines connecting the squares merely represent signal relationships. 8. In the regulation of boiler combustion, the method commonly used for adjusting air volume is ( ). A. Uniform regulation system ； B. Ratio control system ； C. Feedforward control system ； D. Three-impulse regulation system 9. When studying dynamic characteristics, ( ) can be regarded as the input to the system’s element. A. Disturbances ； B. Control is effective ； C. Interference effects and control effects ； D. Signals from measuring instruments 10. The correct choice for the type of anti-surge control valve used in compressors is ( ). A. Valve-mounted type ； B. Air-operated type ； C. Air-shut type ； D. Post-valve type 11. For the single- and double-seat control valves produced in China, the R value is generally ( ). A. 10 ； B．30 ； C. 50 12. ( ) operates in a scanning manner. A. Programmable logic controller ； B. Industrial computer ； C. Ordinary PC ； D. Microcontroller 13. For Siemens PLCs, FB stands for ( ). A. Function block ； B. Tissue block ； C. Function call ； D. Data blocks: 1.A 2.A, D 3.C 4.B 5.B 6.A 77.B 8.B 9.C 10.C 11.B 12.A 13.A 14. The only direction in which a hydraulic jack may be used during operation is ( ). A. Horizontal ； B、Vertical ； C. Tilt ； D. Any direction 15. To analyze the distribution of quality data, use ( ). A. Control chart ； B. Pareto chart ； C. Histogram ； D. Cause-and-effect diagram 16. Special processes refer to ( ). A. Processes that require special skills or techniques ； B. Processes with special quality requirements ； C. Processes whose processing quality cannot be determined through subsequent product verification and testing ； D. Key processes 17. The direction of fluid flow in a rotameter is ( ). A. From top to bottom ； B. Bottom-up ； C. All of them. 18. When using the pressure method to measure the liquid level in an open container, the height of the liquid level depends on ( ). A. Pressure tapping location and container cross-section ； B. Location of the pressure tapping point and medium density; C. Medium density and cross-sectional area. 19. During actual operation, the valve position of the control valve should be at ( ) for optimal performance. A、30%～80% ； B, 15%～90% ； C、20%～100% 20. A pneumatic valve actuator shows no output pressure despite an input signal; what do you think are the main causes? ( ) A、Faults such as sticking of the valve internals ； B. Amplifier failure ； C. Nozzle baffle fouling 21. To control fluids with high viscosity, fibers, and fine particles, which option is the most suitable? A. Butterfly valve ； B、Sleeve valve ； C、Straight-through two-seat valve ； D. Eccentric rotary valve. 22. The sensor of the ST3000 series intelligent transmitter is ( ). A. Silicon capacitor ； B. Compound semiconductors ； C. Silicon resonance: 23. The response time of double-flange transmitters is longer than that of ordinary transmitters. In order to reduce the transmission time of flange transmitters, the ambient temperature of the transmitter ( ) A. should not be too low ； B. It should not be too high ； C. It must remain constant. 14. B 15. C 16. C 17. B 18. B 19. A 20. B, C 21. D 22. B 23. A 24. There is a flange with the specification ANSI 150 LB 3″; its actual operating pressure is ( ). A. 150 LB ； B、Greater than 150LB ； C. It may be greater than or less than 150 LB. 25. When the gas to be analyzed contains solid or liquid impurities, the elevation angle between the axis of the sampling component and the horizontal line should be greater than ( ) degrees. A, 20 ； B, 15 ； C, 30 ； D、45 26. In the block diagram of a cascade control system, there are ( ). A、two controllers ； B. Two transmitters ； C. Two control valves ； D. Two objects under test ； E. Two given values: 27. Quality management is an important part of an organization’s ( ) activities. A. Functional management ； B. Professional management ； C. Comprehensive management ； D. Economic Management 24.C 25.B 26.A, B, D, E 27.C 1. According to the method of expressing errors in terms of numerical values, errors can be classified as (A, B, C): A. Absolute error B. Relative error C. Reference error D. Systematic error 2. A standard pressure gauge is used to calibrate two other pressure gauges, A and B. The reading on the standard gauge is 1 MPa, while the readings on gauges A and B are 1.01 MPa and 0.98 MPa respectively. What are the correction values for these two local pressure gauges? (A, D) A. –0.1 B. 0.1 C. –0.2 D. 0.2 3. The accuracy level of a 1.5-grade instrument can be expressed as (A, C, D): A. 1.5 grade B. +1.5 grade C. 1.5 D. 1.5 4. The accuracy level of an instrument refers to its (E): A. Error B. Basic error C. Maximum error D. Allowable error E. Basic error and maximum allowable value 5. The main quality indicators used to assess the performance of an instrument are (A, B, C, D): A. Accuracy B. Non-linear error C. Heterogeneity D. Sensitivity and sensitivity limit E. Dynamic error 6. The type of error that cannot be controlled is (C): A. Careless error B. Gradual change error C. Random error D. Systematic error 7. The steam pressure associated with heat tracing generally does not exceed (B) MPa. A. 0.5 MPa B. 1.0 MPa C. 1.5 MPa D. 2.0 MPa 8. There are many ways to resist interference, and twisted pair is one of those methods (B). A. Physical isolation B. Reducing magnetic interference C. Shielding D. Demagnetization 9. When flushing the differential pressure measurement pipeline, (C) should be opened first. A. Secondary valve B. Drain valve C. Balancing valve D. Primary valve 10. When the measurement range is around 1000°C, the most suitable thermometer to use is (B). A. Optical pyrometer B. Platinirhodium 10-platinum thermocouple C. Nichrome-nickelsilicon thermocouple D. Platinegermanium 30-platinum thermocouple 11. Under a step increase in steam flow rate, the drum water level ( A ). A. A \"false water level\" appears. B. It rises immediately. C. It drops immediately. D. It remains unchanged. 12. For a vernier caliper with a precision of 1/20, the difference between each scale mark on the main scale and those on the vernier scale is (C). A. 0.5mm B. 0.1mm C. 0.05mm D. 0.01mm 13. When the wire of a thermocouple is broken, the temperature reading will be at (B). A. 0℃ B. the mechanical zero point C. the maximum value D. the original measurement value remains unchanged. 14. The output voltage of a thermocouple is related to (C). A. Temperatures at both ends of the thermocouple B. Temperature at the hot end of the thermocouple C. Temperatures at both ends of the thermocouple and electrode material D. Temperatures at both ends of the thermocouple, electrode material, and length. 15. The principle of temperature measurement using a thermocouple is based on (C). A. Thermal resistance effect B. Thermomagnetic effect C. Thermoelectric effect D. Thermo-pressure effect 16. The resistance value of Pt100 at 0°C is (D). A.0Ω B.53Ω C.101.1Ω D.100Ω 17. After a compensation bridge is used in a thermocouple temperature measurement system, the cold junction temperature is effectively fixed at (C). A. 0℃ B. The temperature at which the compensation bridge is located C. The equilibrium temperature of the compensation bridge D. Ambient temperature. 18. Which of the following has a negative temperature coefficient? (D) A. Pt100 B. Pt10 C. Cu50 D. Thermistor 19. The model of a bimetallic thermometer is (C). A.WNG B.WNY C.WSS D.WTZ 20. A 1151 pressure transmitter has a range of 0–300 kPa; if its zero point shifts upward by 50%, then the instrument’s effective range will be (B). A. 150 kPa B. 300 kPa C. 450 kPa D. 250 kPa 21. If a pressure gauge has a range of 0–16 kgf/cm2 and it is required that the absolute error in the measured value be no more than +0.2 kgf/cm2, then which grade of gauge should be used? (1 kgf/cm2 = 105 Pa) A. Grade 1.0 B. Grade 1.5 C. Grade 2.0 D. Grade 0.5 22. Which of the following belong to electrical level measurement instruments? (A B C D) A. Resistive type B. Capacitive type C. Inductive type D. Thermistive type 23. A pressure-type level transmitter installed below the lowest liquid level in a device must use (A) in order to ensure accurate measurement. A. Positive transfer B. Negative transfer C. Gamma rays D. X-rays 24. Those that belong to variable buoyancy level gauges are (C). A. Float level gauge B. Lever-type float level gauge C. Barrel float level gauge D. Flip plate level gauge 25. The correct statement regarding the proportionality and integration time of a regulator is (B). A. The greater the proportionality gain, the stronger the proportional action. B. The smaller the integration time, the stronger the integral action. C. The greater the proportionality gain, the weaker the proportional action; the larger the integration time, the stronger the integral action. D. The smaller the proportionality gain, the weaker the proportional action; the smaller the integration time, the weaker the integral action. 26. Common methods for experimentally determining the characteristics of a system include (A, C, D). A. Step response curve method B. Least squares method C. Frequency characteristic method D. Rectangular pulse method 27. The feedback signal in a control system that amplifies the original signal is called (B). A. Negative feedback B. Positive feedback C. Feedforward D. Feedback 28. In the block diagram of a regulator, the comparator serves as the point where signals are combined; its output is equal to the input multiplied by (A). A. Algebraic sum B. Integral C. Arithmetic sum D. Product 29. The block diagram of a typical control system consists of elements such as (A, B, C, D, E). A. Regulator B. Sensing element C. Process variable D. Control valve E. Comparing mechanism 30. In the block diagram of a control system, the signals that are connected to the process variable block are (B C E). A. Given value B. Parameter to be adjusted C. Disturbance D. Measured value E. Control parameter 31. A closed-loop automatic control system can be a ( A B C ). A. Feedback regulation system B. Negative feedback regulation system C. Positive feedback regulation system D. Static feedforward regulation system 32. Whether a system is stable depends on (C). A. Input of the system B. Output of the system C. Structural parameters of the system itself D. Initial conditions of the system 33. In a cascade control system, the secondary regulator usually adopts a (C) control law. A.PI B.PID C.PD D.P 34. In a split-range control system, the segmentation of the signal ranges for the two valves is achieved by (C). A. Regulator B. Electrical converter C. Valve positioner D. Transmitter 35. The block diagram of a cascade control system includes (A B C D). A. Two regulators B. Two transmitters C. Two control valves D. Two controlled processes 36. Step control is applied in (A, B, D). A. Expanding the adjustable range of control valves. B. Meeting process requirements for controlling two different media in one control system. C. Being used for systems with large amplification factor variations. D. Safety measures for production. E. Being used for systems with high time lags. 37. Which of the following DCS systems are products of Honewell Company? (A, B) A.TDC-3000 B.S9000 C.INFI-90 D.MOD-300 38.The DCS control system is also known as (B D). A. Centralized control system B. Distributed control system C. Computer control system D. Distributed Control System 39. The optimal ambient temperature and optimal relative humidity for a DCS system are respectively (D). A. (15+5)°C, 40%~90% B. (20+5)°C, 20%~80% C. (25+5)°C, 20%~90% D. (20+5)°C, 40%~80% 40. Distributed control systems make use of the latest achievements in modern high technology: (A B C D). A. Computer technology B. Communication technology C. CRT technology D. Automatic control technology 1. A flow rate is measured using a differential pressure transmitter in combination with a standard orifice plate; which of the following situations could cause the reading on the secondary instrument to increase? __①③__. ① There is a control valve at 5D, in the straight pipe section upstream of the throttle element. ② The orifice plate is installed in the wrong direction. ③ The eccentricity of the throttle component installation exceeds the specified value. ④ Polarity is reversed. 2. To measure a current of 8mA using the following ammeters, the most accurate result is obtained with __①__. ① 0.5 grade 10mA meter ② 0.2 grade 50mA meter ③ 0.5 grade 20mA meter. 3. Among the following control loops, which one makes use of the PID control method most frequently? _①___ ①Temperature control circuit ② Pressure control circuit ③ Flow rate control circuit ④ Level control circuit. 4. For level measurement instruments equipped with a three-valve assembly, which of the following situations cause the indication to be low? _①③ __ ①① Leakage in the pressure guide tube or valve on the positive pressure side ② Leakage in the pressure guide tube or valve on the negative pressure side ③ Leakage in the balance valve ④ Blockage in the pressure guide tube on the negative pressure side. 5. Which of the following statements about the function of valve positioners are correct? ① and ③: ① Changing the flow characteristics of the valve; ② Changing the direction of fluid flow; ③ Enabling step control; ④ Extending the service life of the valve. 6. In the parameter tuning of pressure control systems, which of the following PI parameter settings are reasonable? _④_. ① P=100% I=1min ② P=80% I=4min ③ P=60% I=0.2min ④ P=50% I=1.5min 7. The standard internal thread for fixing the temperature sensing boss is (①). ①M27×2 ② M30×2 ③ 1\"　　　④1/2\" 8. The standard volumetric flow rate of Nm3/h refers to the flow rate when converted to the conditions of (②). ①0℃, 760mmHg ② 20℃, 760mmHg ③ 4℃, 760mmHg ④ 25℃, 760mmHg. 9. The basis for determining the forward and reverse actions of a regulator in a control system is ___② _. ① ② Implementing positive feedback in the closed-loop circuit. ③ Implementing negative feedback in the closed-loop circuit. ④ The system’s gain should be appropriate. ⑤ Safety in production. 10. The optimal installation location for the body of a double-flange transmitter used for level measurement is (③). ① Between the positive and negative pressure flanges. ② Above the negative pressure flange. ③ Below the positive pressure flange. 11. In a cascade control system, the choice of the forward or reverse action mode for the main controller depends on (④). ① The control valve. ② The secondary controller. ③ The secondary process variable. ④ The primary process variable. 12. The DCS systems that are of domestic origin are (②③④). ①TDC3000　　　②HS2000　　③SUPCON-JX　　④FB-2000 13. Which of the following materials has the strongest shielding effect against gamma rays? (③) ①Steel　　　②Concrete　　③Lead　　④Mercury 14. The effect of changes in atmospheric pressure on calibrating absolute pressure transmitters (①). ①Yes　　　②No 15. In flow measurement, temperature compensation and pressure compensation are generally used; such compensation corrects （①）errors. ①Systematic error ； ②random error ； ③negligence error ； ④Random error 16: The accuracy class of a instrument refers to the (⑤) of that instrument. ①error ； ②Basic error ； ③Maximum error ； ④allowable error ； ⑤The maximum allowable value for the basic error is 17; the errors that we cannot control are (②④). ①Systematic error ； ②random error ； ③negligence error ； ④Random error 18: The thread types for the connections of transmitters and ordinary pressure measuring instruments are generally (①). ①M20×1.5 ② M22×1.5 ③ M16×1.5 ④ M27×2. 19. When the temperature range is around 1000 degrees, the most suitable thermometer to use is (②). ①Optical pyrometer ； ②Platinum-rhodium 10-platinum thermocouple ； ③Nickel-chromium – nickel-silicon thermocouple ； ④Platinum-rhodium 30–platinum-rhodium 6 thermocouples; 20. The positive terminal of the KX extended thermocouple compensation wire is red, while the negative terminal is (③). ①Green ； ②Purple ； ③Black ； ④White 21. The temperature measurement principle of thermocouples is based on (④). ①Thermal resistance effect ； ②theromagnetic effect ； ③Thermopressure effect ； ④Thermoelectric effect 22: The absolute zero is (④) °C. ①273 ； ②0 ； ③273.15 ； ④－273.15 23. The feedback signal in a control system that amplifies the original signal is called (②). ①Negative feedback ； ②positive feedback ； ③feedforward ； ④Feedback 24: A proportional control system generally has (②) control valves. ①1 ； ②2 ； ③3 ； ④4 25. For safety reasons, the feedwater control valve for the drum should be a （②） type control valve. ①Air-operated ； ②For air-shut type 26, the operating temperature of PTFE packing is generally (①). ①-40～250℃ ； ②-60～450℃ ； ③-60–-250°C 27. Valve positioners are generally composed of components such as cams, range settings, and zero positions; the component that can change the stroke characteristics of the valve is (①). ①cam ； ②Range component ； ③Zero component 28: When using a thermistor to measure temperature, the reason why the reading shown on the instrument is lower than the actual value or is unstable cannot be (④). ⑴ There are metal shavings or dust inside the protective tube ； ⑵Dust accumulation between terminals ； ⑶Thermal resistor short circuit ； ⑷The thermal resistor is open-circuited. 29. When measuring the liquid level in an open container using the pressure method, the level of the liquid depends on (②) ① the location of the pressure measurement point and the cross-sectional area of the container; ② the location of the pressure measurement point and the density of the fluid; ③ the density of the fluid and the cross-sectional area. 30. When using a double-flange instrument to measure the liquid level in a container, and both the zero point and the range of the instrument are standard, if the instrument is installed at a higher position, then the instrument (④) ① has its zero point increase while the range remains unchanged; ② has its zero point decrease while the range remains unchanged; ③ has its zero point remain unchanged while the range increases; ④ has neither its zero point nor its range change. 1. The function of a multimeter: (Model 500 or 30, as well as ordinary multimeters). (2) 1) Measure the length of the wire. 2) Measure the resistance of the component. 3) Measure the oxygen content in the air. 4) Measure the weight of the object. 2. The positive terminal of a multimeter’s battery is: (1) 1) The ground terminal. 2) The positive terminal (the end with the red test lead). 3. Which of the following tools are used to measure 4–20mA current signals? (2) 1) Screwdriver. 2) Multimeter. 3) Calibrator (for pressure). 4) Voltage tester. 4. The voltage value of 220VAC can be measured using which of the following tools? (3) 1) 24V DC power supply. 2) Voltage tester. 3) Multimeter in AC mode. 4) Calibrator (for pressure). 5. To check whether there is electricity present in 220VAC alternating current, which of the following tools can be used? (3, 4) 1) Multimeter R mode 2) Multimeter DC mode 3) Multimeter AC~ mode 4) Voltage tester. 6.1~5VDC is powered by the following. (3) 1) 24V DC power supply 2) Multimeter 3) 1–24V DC power supply 4) 24V AC power supply. 7. What is meant by direct current and alternating current is: (3) 1) 24V electricity 2) 220V electricity; alternating current that has been rectified and filtered becomes direct current. 8. Examples of direct current include: (1, 2, 3, 4) 1) 1V 2) 5V 3) 24V 4) 220V. 9. The power supply for thermocouples is: (1) 1) Direct current 2) Alternating current 3) Three-phase alternating current 4) No power supply. 10. To troubleshoot instrument faults, one needs: (1, 3) 1) Instrument repair technician 2) Process operator 3) Relevant tools. 11. For a measurement transmitter with a range of 6MP, when the transmitter displays 50%, the measured output value should be ； (4) 1) 1MP 2) 2MP 3) 3MP 4) 4MP 12. A Type III differential pressure transmitter powered by 12VDC – can it operate properly? (3) 1) Yes 2) Abnormal display 3) No 4) It depends on the specific situation. 13. Which of the following symbols represents an electrical converter? (2) 1) FE 2) FY 3) FT 4) FV 14. The isolation fluid should be filled in: (3) 1) Within the tank itself 2) In the process pipelines 3) In the isolation tank 15. Among measurement errors, those expressed as numerical values can be classified as: (1,2) 1) Absolute error 2) Relative error 3) Random error 4) Static error 16. Based on the pattern in which errors occur, they can be classified as: (2) 1) Absolute error 2) Systematic error 3) Static error 4) Random error 17. Depending on the conditions under which the instrument is used, errors can be classified as: (3) 1) Relative error 2) Negligible error 3) Fundamental error 18. According to the relationship between the measured variable and time, errors can be classified as: (1,2) 1) Static error 2) Dynamic error 3) Relative error 4) Negligible error 19. Based on their relationship with the measured variable, errors can be classified as: (2) 1) Systematic error 2) Fixed-value error 3) Additional error 4) Negligible error 20. (2) represents the difference between the measurement result and the true value. 1) Relative error 2) Absolute error 3) Fundamental error 21. The accuracy class of a instrument is determined based on reference (3). 1) Precision 2) Grade 3) Error 22. System error is also known as (1). 1) Systematic error 2) Precision grade 3) None of them 4) All of them 23. Negligible error is also known as (1). 1) Gross error 2) Fine error 3) Medium error. 24. A pressure gauge is considered qualified only when its maximum allowable error (2), that is, its accuracy class, meets the specified standards. 1) Greater than 2) Less than 3) Equal to 25. The upper limit of the measurement range, which is 0~100 degrees Celsius, is (3). 1) 0 degrees Celsius 2) 50 degrees Celsius 3) 100 degrees Celsius 26. The measurement range is -100 to -20 degrees Celsius, and its scale is (3). 1) -100 degrees Celsius 2) -20 degrees Celsius 3) 80 degrees Celsius 27. The accuracy class of a 1.5-grade instrument can be expressed as: (1) 1) 1.5 grade 2) +-1.5 grade 3) +1.5 grade 4) 1.5 28. The accuracy class of an instrument refers to the instrument’s (4) 1) error 2) basic error 3) allowable error 4) maximum allowable value of the basic error 29. The accuracy class is a classification of instruments based on their (2) level of precision. 1) Precision 2) Accuracy 3) Limit 30. The output range of a pressure transmitter is 20~100 KPa; therefore, the maximum value it can measure is (3) 1) 99.999 KPa 2) 101 KPa 3) 100 KPa 4) 20 KPa 31. Sensitivity refers to the degree to which a measuring instrument is sensitive to changes in the parameter being measured (2). 1) Incorrect 2) Correct 3) Not necessarily correct 32. What is the dead zone of a meter expressed in terms of the input range? (1). 1) Percentages 2) Fractions 3) Decimals 4) Integers 33. The higher the sensitivity value, the more sensitive the instrument is. (1) 1) Correct 2) Incorrect 3) Not necessarily correct. 34. Pressure is (2) a force that acts uniformly on a unit area. (2) 1) Horizontal 2) Vertical 3) Diagonal 35. The unit of pressure is (3). 1) N Newtons 2) Kg kilograms 3) Pa Pascals. 36. Does the ambient temperature affect the measurement accuracy of the owner’s press? (2). 1) None 2) Yes 3) None of the above 37. When calibrating an electric contact pressure gauge, is it necessary to check its indication accuracy? (2). 1) Not necessarily 2) Must 3) Not required 38. Is there an alarm limit for electric contact pressure (1)? 1) Yes 2) No 3) Not necessarily 39. Flow rate refers to the amount of fluid that passes through a certain cross-sectional area of a pipe (2). 1) Per unit volume 2) Per unit time 3) Per unit area 40. When a fluid flows, internal friction within the fluid arises due to the interaction between its flow layers, which gives the fluid viscosity; this is known as the fluid’s (2). 1) Liquid level 2) Viscosity 3) Flow rate 4) Internal resistance 41. The compression coefficient of ordinary gases is plotted as a curve based on certain values; thus, to determine this value, one can simply refer to the corresponding curve. (3) 1) Theoretical calculation 2) Formula-based calculation 3) Experiment 42. Under the same pressure difference, the name of the throttling device with the greatest pressure loss is (2). 1) Nozzle 2) Orifice plate 3) Venturi tube 43. The name of the throttling device used for measuring large-diameter pipes with low fluid pressure inside is (3). 1) Nozzle 2) Orifice plate 3) Venturi tube 44. What is another name for taking pressure readings from the flange of an orifice plate? (1) 1) 1-inch flange method 2) 2-inch flange method 3) 5-inch flange method 45. Since both end faces of a symmetric orifice plate have no conical angles and the technical requirements for these two end faces are the same, the flow direction of the orifice plate is not fixed. (2) 1) Incorrect 2) Correct 3) Not necessarily correct 47. When the same pressure is applied to both the positive and negative chambers of a differential pressure transmitter, the output zero point of the transmitter shifts; this shift value changes as the static pressure increases. What is called this error caused by static pressure? (1) 1) Static pressure error 2) Relative error 3) Fundamental error 48. Capacitive, string vibration, diffused silicon, and other types of transmitters are part of the new generation of transmitters, and their advantages are. (1, 2, 3, 4) 1) Simple structure 2) High precision 3) Wide measurement range with low static pressure error 4) Easy to adjust and use. 49. The 1151 differential pressure transmitters with different measurement ranges differ due to the (1) of their measuring diaphragms. 1) Different thicknesses 2) Different materials 3) Different diameters. 50. The different measurement ranges of lever-type differential pressure gauge transmitters are mainly due to (3) of their measuring diaphragms. 1) Different thicknesses 2) Different materials 3) Different diameters. 51. When installing a capacitive differential pressure transmitter, attention should be paid to (1, 2): 1) Severe vibration 2) Corrosion. 52. If the positive and negative pressure conduits of a capacitive differential pressure transmitter are in the opposite direction to those of the positive and negative pressure chambers, it is not necessary to modify the pressure conduits; simply rotate the electrical components by a small angle with respect to the measuring diaphragm box (3) 1) 90 degrees 2) 360 degrees 3) 180 degrees. 53. What should be done if the positions of the vent and drain valve holes on the transmitter flange base are incorrect? (1) 1) The positive and negative flange bases can be swapped. 2) The positive and negative electrodes can be swapped. 54. What should not be done when calibrating a capacitive differential pressure transmitter? (4) 1) Zero adjustment 2) Range adjustment 3) Linearity adjustment 4) Power off. 55. The possible reasons for no output from a capacitive differential pressure transmitter are (1,2): 1) No voltage supply 2) No pressure difference 3) Poor linearity. 56. The relationship between the density of a liquid and its mass is (2): 1) Unrelated 2) Directly proportional (at constant volume) 3) Inversely proportional (at constant volume). 57. The basic unit of density is (1): 1) Kg/m3 2) N/cm3 3) Kg/m2. 58. When using the pressure method to measure the level of liquid in an open container, the level depends on (2). 1) Location of the pressure tapping point and the container’s cross-section 2) Location of the pressure tapping point and the density of the medium 3) Density of the medium and the cross-section. 59. When using the differential pressure method to measure the liquid level in a container, the level is determined by (3): 1) The pressure difference between the upper and lower points of the container 2) The pressure difference, the container’s cross-sectional area, and the density of the medium 3) The pressure difference, the density of the medium, and the location of the pressure tapping point. 60. In buoyant level gauges, those that operate based on Archimedes’ principle are (1): 1) Floats 2) Buoy balls. 61. In a float-type steel belt level gauge, if there is a change in the liquid level but the pointer does not move, the possible causes are (1, 2): 1) Wear of the gears in the display mechanism 2) Looseness between the sprocket and the shaft of the display mechanism 3) Loose pointer 4) Bending of the guiding protective tube. 62. Possible reasons for errors in the readings of a float-type steel belt level gauge are (2, 3): 1) Wear of the gears in the display mechanism 2) Loose pointer 3) Insufficient torque from the constant-force spring or magnetic couple. 63. If the float in a torsion tube float level gauge breaks, the instrument will indicate (2): 1) Maximum value 2) Minimum value 3) Indeterminate value. 64. If the float in a torsion tube float level gauge comes loose, the instrument will indicate (1): 1) Maximum value 2) Minimum value 3) Unchanged value. 65. For a torsion tube level gauge of the same model, the larger the measurement range, the (3) the diameter of the float: 1) Larger 2) Unchanged 3) Smaller. 66. As the liquid level rises from the lowest to the highest point, the buoyant force acting on the float (1): 1) Increases 2) Decreases 3) Remains unchanged. 67. In automatic control systems, the differential time is generally represented by (3): 1) P 2) I 3) D. 68. For liquids that do not crystallize or become viscous at the operating temperature but may do so at ambient temperature, (1) should be used: 1) Internal float level gauge 2) External float level gauge 3) Either one is acceptable. 69. For liquids in process equipment where shutdowns should be avoided as much as possible, (2) should be used: 1) Internal float level gauge 2) External float level gauge 3) Either one is acceptable. 70. For liquids with large fluctuations, (2) should be used: 1) Internal float level gauge 2) External float level gauge 3) Either one is acceptable. 71. The equilibrium temperature between gas and liquid phases is called (2): 1) Melting point 2) Boiling point 3) Freezing point. 72. The equilibrium temperature between solid and liquid phases is called (3): 1) Melting point 2) Boiling point 3) Freezing point. 73. The equilibrium temperature among solid, liquid, and gas phases is called (3): 1) Boiling point 2) Freezing point 3) Triple point. 74. The equilibrium temperature between ice and air is called (1): 1) Freezing point 2) Melting point 3) Boiling point. 75. What is the boiling point of water in absolute terms? (3): 1) -273.16 2) 273.16 3) 373.15 4) 100. 76. Commonly used filling fluids in glass liquid thermometers are (1, 2): 1) Mercury 2) Organic liquids 3) Inorganic liquids. 78. The lower measurement limit of a glass liquid thermometer is determined by what property of the filling fluid? (2): 1) Boiling point 2) Freezing point 3) Thermal conductivity. 79. To increase the upper measurement limit of a mercury thermometer, a certain pressure of (2) is usually introduced above the filling fluid inside the capillary: 1) Air 2) Inert gas 3) Oxygen. 80. In pressure-type thermometers, the greater the coefficient of thermal expansion of the filling material, the (1) the instrument becomes: 1) More sensitive 2) Less sensitive 3) Unaffected. 81. In pressure-type thermometers, the longer the capillary, the (2) the response time of the instrument becomes: 1) Faster 2) Slower 3) Unchanged 4) Irregular. 82. When using a thermocouple for temperature measurement and the reading is inaccurate, a millivolt meter should be used to measure its (1): 1) Voltage 2) Current 3) Capacitance 4) Resistance. 83. To extend the length of a thermocouple, (3) is used: 1) Wires 2) Three-core cables 3) Compensation wires 4) Two-core cables. 84. When using a thermocouple with a K-type rating along with its matching compensation wire to measure temperature, but if the polarity of the compensation wire is reversed during wiring, the instrument’s indication will be (3). 1) Too large 2) Too small 3) It may be large or small, depending on the specific circumstances. 85. The higher the temperature, the more (1) the resistance value of materials such as platinum, nickel, and copper. 1) Large 2) Small 3) Unchanged 86. The resistance value of a Pt100 platinum resistor at 0 degrees is (3). 1) 0 ohms 2) 0.1 ohms 3) 100 ohms 4) 108 ohms 87. In a thermistor thermometer, the relationship between resistance and temperature is (1). 1) Nearly linear 2) Non-linear 3) Horizontal straight line. 88. Common compensation wires are used to introduce the thermocouple potential into temperature measuring instruments; does the length of the compensation wire have an impact on its measurements? (2) 1) There is an impact. 2) No impact. 3) It depends on the specific circumstances. 89. In FRCAS101, FRCAS stands for (1) 1) Flow rate recording, adjustment, and alarm interlock; 2) Flow rate display, interlock, and alarm control; 3) Flow rate adjustment, display, recording, and interlock. 90. How to select thermocouples and thermal resistors (1). 1) Select based on the temperature measurement range. 2) Select based on the ambient temperature. 3) Select based on the object being measured. 91. The feedback control system is a closed-loop system (3). 1) Not necessarily 2) No 3) Yes 92. How are constant-value control systems, program-controlled systems, and follow-up control systems classified? (3) 1) According to the structure of the automatic control system 2) According to the characteristics of the automatic control system 3) According to the pattern of change in the set value. 93. In the field of automation, the unbalanced state in which the controlled variable changes over time is referred to as (3). 1) Action 2) Movement 3) Dynamics 94. The relationship between static and dynamic in automatic control systems (2). 1) It is a linear relationship. 2) Static is a special case of dynamic. 3) Non-linear relationship. 95. In computer control systems, the input and output signals of the computer are (2). 1) Analog signal 2) Digital signal 3) 4–20mA standard signal 96. In a computer control system, the host and peripheral devices are (1). 1) Hardware part 2) Software part 3) Intermediate part 97. In a computer control system, after receiving field signals and performing calculations, judgments, and processing, the host makes various control decisions; in what form are these decisions outputted? (3) 1) Decimal 2) Hexadecimal 3) Binary 98. Computer software includes (3). 1) External devices 2) Various instruments 3) Programs written in various languages, etc. 99. In a DCS system, DO stands for: (3) 1) Analog input 2) Analog output 3) Digital output 100. The BASIC language belongs to (1, 3). 1) Computer software 2) Computer hardware 3) Computer languages 101. The correct installation of compensation wires should start from the thermocouple and extend to (3). 1) On-site junction box 2) Secondary instruments 3) A location at the same temperature as the cold-end compensation device. 102. Automatic control valves are suitable for (1, 2) applications. 1) Small flow variation 2) Low requirements for regulation accuracy 3) Easy supply of instrument air. 103. Adding differential action to the regulator is used for (3). 1) Overcome the pure time lag of the object 2) Overcome the inertial time lag of the object 3) Overcome both the inertial time lag and the easy time lag of the object. 104. Temperature and pressure correction in flow measurement using throttling devices is used to correct (　3　). 1) Random error 2) Relative error 3) Systematic error 4) Accidental error 105. When using an orifice plate to measure flow, the orifice plate should be installed (　1　) in front of the control valve. 1) In front 2) Behind 3) At any position 106. The operating range of a pressure gauge is generally between 1/3 and 2/3 of its full scale; if the pressure is below 1/3 of this range, then (　3　). 1) The accuracy level decreases 2) There is no indication due to too low a pressure 3) The relative error increases. 107. The determination of the forward and reverse actions of the regulator in a control system is based on (　2　). 1) Safety in production 2) Achieving negative feedback in the closed-loop system 3) An appropriate gain for the system. 108. Those that do not require cold-junction compensation are (1, 3): 1) Copper resistors 2) Thermocouples 3) Platinum resistors. 109. When using a thermocouple with a K calibration type along with a matching compensation wire to measure temperature, but if the polarity of the compensation wire is reversed during wiring, the instrument reading will be (3). 1) High 2) Low 3) It could be high or low, depending on the specific circumstances. 110. Can direct control of the control valve using a transmitter output achieve regulation? (3) 1) Yes 2) No 3) It depends on the control requirements. 111. The value of the proportional band in a certain control system is already fairly appropriate; when integral action is added (2). 1) Appropriately reduce the proportional band. 2) Appropriately increase the proportional band. 3) No change is needed to the proportional band. 112. When using a single-flange level gauge to measure the liquid level in an open container, and after the gauge has been calibrated but its installation position is lowered due to maintenance needs, the gauge reading will be (1). 1) Rising 2) Falling 3) Unchanged 113. For a PMK regulator that is in use, if the power supply is suddenly interrupted and then restored, the output value of the regulator after restoration will be (1). 1) Value just before power outage 2) Preset value 3) 0% 114. The commonly used type of low-noise control valve is (2). 1) Single-seat valve 2) Sleeve valve 3) Diaphragm valve 4) Corner valve. 115. The addition of differential action to the regulator is mainly used for (3). 1) Overcome the pure time lag of the object 2) Overcome the inertial time lag of the object 3) Overcome both the inertial time lag and the easy time lag of the object. 116. It is reasonable to use an orifice plate to measure flow rate, with the orifice plate installed on the control valve (1). 1) Front 2) Back 3) Any position. 117. Temperature and pressure correction in flow measurement using a throttling device is a form of correction (4). 1) Random error 2) Relative error 3) Accidental error 4) Systematic error. 118. In a differential pressure flow meter, if the negative pressure pipeline is blocked, the gauge will indicate (1). 1) Too large 2) Too small 3) Unchanged 119. There are two constant orifice plates, with the same diameter; however, the length of orifice A is greater than that of B. Under the same pressure difference, the air resistance of A is (1) that of B. 1) Greater than 2) Less than 3) Equal to 120. Determine which of the following control objects has the greatest lag. (3) 1) Tank level 2) Temperature of the direct steam heater 3) Pipeline pressure 4) Pipeline flow rate. 121. The stability of the control system is the most fundamental requirement for it; the attenuation rate Ψ of the stable control process should be: (3) 1) Ψ=0 2) Ψ

Calculation problems: 1. There is a temperature measuring instrument with a scale range of 0–400°C. Given that its maximum absolute error is tmax = 5°C, what is its relative percentage error? 2. A bridge with an accuracy class of 0.5 has a lower scale value that is negative and corresponds to 25% of the full scale range. The allowable absolute error for this instrument is 1°C. Determine the upper and lower limits of its scale. 3. There are two temperature measuring instruments with measurement ranges of 0–800°C and 600–1100°C respectively. Both have a maximum absolute error of ±6°C each. Determine their accuracy classes. 4. A pressure gauge with an accuracy class of 1.5 and a scale range of 0–100 kPa was tested. It was found that the error at 50 kPa is the greatest, at 1.4 kPa; errors at other scale points are all less than 1.4 kPa. Is this pressure gauge qualified? 5. There is a pressure gauge with a range of 320–360 kPa. If the following two pressure transmitters, A and B, are used for measurement, which one will provide more accurate readings under normal conditions? Pressure Transmitter A: Class 1, 0–600 kPa ； Pressure transmitter B: Class 1, 250–500 kPa. 6. What is the pressure generated by a 6.1 m water column at 4°C and under standard gravitational acceleration? 7. A pressure gauge has an accuracy of Class 0.5 and a measurement range of 0–500 kPa; what is its maximum allowable error? 8. A pressure transmitter with a measurement range of 0–200 kPa is being calibrated. What is the output current when the input pressure is 150 kPa? 9. There is a standard Bourdon tube pressure gauge with a range of 0–100 kgf/cm2 and an accuracy of Class 1.5. The calibration results are as follows. Is this gauge qualified? Standard values (kgf/cm2): 0, 25, 50, 75, 100. Measured values (kgf/cm2): Forward stroke: 0.1, 24.6, 49.8, 74.2, 99.8; Reverse stroke: 0.3, 25.8, 50.1, 75.8, 100. Note: 1 kgf/cm2 ≈ 105 Pa. 10. A vacuum pressure gauge has a range of –100–500 kPa. During calibration, the maximum error occurs at 200 kPa; the readings on the calibration gauge are 194 kPa during the forward stroke and 205 kPa during the reverse stroke. Does this gauge meet the accuracy requirement of Class 1.0? 11. An 1151 absolute pressure transmitter has a range of 0–80 kPa (absolute pressure). Calibration is carried out using a standard vacuum pressure gauge with a range of 100–0 kPa. If the local atmospheric pressure is 98 kPa, what is the reading indicated by the vacuum pressure gauge when the transmitter outputs 12 mA? 12. A level gauge has a measurement range of 0–1000 mm. If the liquid level is measured to be 445 mm, what percentage of the range does this represent? 13. In the blow-out level gauge shown in the figure, if ρ = 1.25 g/cm3 and the pressure gauge indicates 49 kPa, what is the liquid level height h? 14. Calculate the calibration range and offset for the pressure-type level gauge shown in the figure, given that hl = 5 m, h2 = 1 m, and ρ = 1.0 g/cm3. 15. The bottom area of the tank shown in the figure is A; the density of the fluid inside the tank is ρl, and the height of the fluid is H. The density of the air inside the tank is ρ2. Determine the mass of the liquid fluid inside the tank. 16. Use the hydrostatic pressure method to measure the liquid level in a tank that is at a high elevation. The gauge reading is 1000 kPa, the density of the fluid is 1.2 g/cm3, and the distance between the pressure sensing point and the instrument is 5 m. Determine the liquid level in the tank at that high elevation. 17. For a pneumatic differential pressure level transmitter with a range of 0–2000 mm, what is the liquid level in millimeters when its output is 0.6 g/cm² (1 kgf/cm² ≈ 105 Pa)?
18. The double-flange level gauge shown in the figure is used to measure the level in a closed container. Given that hl = 20 cm, h2 = 20 cm, h3 = 200 cm, and h4 = 30 cm, with the density of the light medium being ρl = 0.8 g/cm³ and that of the heavy medium being ρ2 = 1.1 g/cm³, and the density of the silicone oil in the gauge’s capillary being ρ0 = 0.95 g/cm³, what are the gauge’s range and zero-point shift?
19. A float level gauge with a float length of 1 m is used to measure the level of a medium with a density of 800 kg/m³. It is calibrated using water with a density of 1000 kg/m³. What is the maximum water filling height during calibration?
20. A float level gauge is used for level measurement. The float’s length is L = 1000 mm, its outer diameter is D = 20 mm, and its weight is 376 g. The density of the medium is 0.8 g/cm³. If calibration is done using weights, what are the weights required at 0%, 25%, 75%, and 100% of the full range?
21. An electric float level transmitter is calibrated using water. The float’s length is L = 500 mm, and the density of the medium being measured is 0.85 g/cm³. Calculate the height of the float submerged in water when the output is 0%, 50%, and 100% (with the density of water taken as 1 g/cm³).
22. A pressure-type level transmitter, as shown in the figure, is used to measure the level in an open container. The density of the medium is ρ = 1200 kg/m³, with hl = 1 m and h2 = 2 m. What are the transmitter’s range and zero-point shift?
23. A double-flange differential pressure transmitter is used to measure the level in a closed container, as shown in the figure. The range of level changes is h = 1 m. In the figure, hl = 2 m, h2 = 1 m, and H = 3 m. The density of the medium being measured is ρl = 1200 kg/m³, while the density of the fluid in the transmitter’s capillary is ρ2 = 850 kg/m³. What are the transmitter’s range and zero-point shift?
24. A blowing-type level gauge is used to measure the level in an open container, as shown in the figure. Given that hl = 20 cm, the density of the medium being measured is 1000 kg/m³, and the pressure reading is 40 kPa, what is the actual liquid level height? 25. There is a proportional control valve whose maximum flow rate under standard conditions is 50 m3/h, and its minimum flow rate is 2 m3/h. If the total travel distance is 3 cm, what is the flow rate at the lcm opening? 26. What is 1/8 inch in millimeters? 27. Given that the temperature of water is 297 K (thermodynamic temperature), calculate what this temperature corresponds to in degrees Celsius. 28. The pressure gauge on the boiler drum reads X, and the barometric pressure gauge reads Y; what is the absolute pressure of the fluid inside the drum? 29. The sinusoidal current in the motor, as measured by an ammeter, is 10 A. What is the maximum value of this current? Additionally, the voltage of the AC power supply, as measured by a voltmeter, is 220 V. What is the maximum value of this voltage? 30. If the minimum resistance of the human body is 800 Ω, and it is known that a current of 50 mA passing through the body can cause respiratory paralysis, preventing the person from breaking free from the power source, what is the voltage in volts? 31. When the temperature of a mercury thermometer is 20°C, the air pressure, as measured by a mercury barometer, is 765 mmHg. Please express this pressure in Pa. 32. A winch is required to perform 50 kW•h of work within 5 hours. Ignoring other losses, what power should the motor have? 33. The pressure gauge reads P_gauge = 0.12 MPa, while the atmospheric pressure, as indicated by the barometer, is 680 mmHg. Determine the absolute pressure of the gas inside the container. 34. What is the equivalent value of a pressure of 10 mmH2O in Pa? 35. If the volume of an oxygen tank is 40 L, what is its equivalent value in m3? 1. δmax = ×100% = 1.25%
2. The range is 1°C/O.005, which equals 200°C; the lower limit is (200°C × 25%) = –50°C. Thus, the scale limits for this instrument are from –50°C to 150°C.
3. Based on the basic error δm = ×100%, we get δm = ×100% = 0.75%; δml = ×100% = 1.2%. According to the accuracy class standards for common industrial instruments, a temperature measuring instrument with a measurement range of 0–800°C should be classified as grade 1 in terms of accuracy ； Thermometers with a measurement range of 600–1100°C should be classified as grade 1.5. 4. The maximum allowable error for this gauge = ×100% = 1.4%. The permissible error of the gauge is 1.5 kgf/cm2; therefore, this gauge does not meet the requirements. 10. The percentage deviation = ×100% = (205–194) / ×100% = 1.83%, which is greater than 1.0%. Hence, it does not satisfy the precision requirements for grade 1.0. 11. When the input pressure to the transmitter is P_abs, and the output current is 12 mA, then P_abs/(80-0)×16+4 = 12, which gives P_abs = 40 kPa. Since P_vacuum = P_atmospheric – P_abs = 98 – 40 = 58 kPa, the reading of the vacuum gauge is 58 kPa, with the transmitter’s output being 12 mA. 12. 445/(1000–0)×100% = 44.5% 13. According to the principle of hydrostatic pressure, P = ρgh; therefore, h = P/ρg = 49/1.25×9.8 = 4 m. 14. As can be seen from the graph, the measurement range of the level gauge is P = ρgh1 = 1.0×9.8×5 = 49 kPa. The displacement A = ρg h2 = 1.0×9.8×1 = 9.8 kPa. Thus, the calibration range of the instrument is 9.8–58.8 kPa. 15. The weight of the liquid in the tank, W1, is equal to mg, and since m = ρ1V = ρ1AH, it follows that W1 = ρ1AHg. As the density of air is ρ2, the buoyant force exerted by the air on the liquid cannot be ignored. The buoyant force W2 = ρ2Vg = ρ2AHg; therefore, the weight of the liquid in the tank is W = W1 – W2 = ρ1Ahg – ρ2Ahg = AHg(ρ1 – ρ2). 16. If the liquid level in the high-level storage tank is h, then the pressure value P is given by P = ρg(h + 5). Hence, h = p/(ρg) – 5 = 100/(1.2×9.81) – 5 = 3.5 m. 17. The output signal of the pneumatic differential pressure transmitter ranges from 0.2 to 1.0 kgf/cm2. When the liquid level is at height H, the output is 0.6 kgf/cm2; thus, H/2000×(1.0–0.2) + 0.2 = 0.6, which gives H = 1000 mm. 18. The range of the instrument is ΔP = h3(ρ2 + ρ3)g = 2×(1.1–0.8)×9.81 = 5.886 kPa. When the interface is at its lowest point, the pressures on the positive and negative sides of the instrument are respectively P+ = P1 + ρ1g(h1 + h2 + h3) + ρ2gh4 – ρ0gh = P1 + 0.8×9.81×(0.2 + 0.2 + 2) + 1.1×9.81×0.3 – 0.95×9.81h = P1 + 22.073 – 9.32h, and P– = P1 + ρ1gh1 + ρ0g(h2 + h3 + h4 – h) = P1 + 0.8×9.81×0.2 + 0.95×9.81(0.2 + 2 + 0.3 – h) = P1 + 24.868 – 9.32h. The displacement A = P+ – P– = –2.795 kPa (negative displacement). 19. To ensure that the buoyant force acting on the float when the density of the liquid medium is 800 Kg/m3 and its height is 1 m is equal to the buoyant force it experiences in water with a density of 1000 Kg/m3, water can be used to calibrate the height of the float. Thus, AL_water × ρ_water × g = AL_medium × ρ_medium × g, where L_water, ρ_water represent the height and density of water, respectively ； L denotes the height of the medium, while ρ denotes its density ； A is the cross-sectional area of the float. Therefore, L_water = ρ_medium × L_medium / ρ_water = 800 × l / 1000 = 0.8 m. 20. A float level gauge is used for measuring liquid levels; the length of the float is L = 1000 mm, its outer diameter is D = 20 mm, and its weight is 376 g. The density of the medium is 0.8 g/cm³. If calibration is carried out using weights, what weights in grams are required at 0%, 25%, 75%, and 100% of the full scale? 21. An electric float level transmitter is to be calibrated using water. It is known that the length of the float is L = 500 mm, and the density of the medium is 0.85 g/cm³. Calculate the height to which the float should be submerged when the output corresponds to 0%, 50%, and 100% of the full scale. (The density of water is taken as 1 g/cm³.) 22. The range of the transmitter is Δp = ρgh² = 1200 × 9.81 × 2 = 23.54 kPa. At the lowest liquid level, the pressure acting on the transmitter is A = ρgh₁ = 1200 × 9.81 × 1 = 11.77 kPa. In other words, the transmitter needs to shift upward by 11.77 kPa. 23. As can be determined from the given information, the range of the transmitter is ΔP = ρ1gh = 1200 × 9.81 × 1 = 11.77 kPa. When the instrument measures the lowest liquid level, the pressures in the positive and negative chambers are respectively P+ = P1 + ρ1gh2 + ρ2gh1 and P- = P1 + ρ2gH + ρ2gh1. Therefore, P+ – P- = ρ1gh2 – ρ2gH = 1200×9.81×1 – 850×9.81×3 = -13.25 kPa. Hence, the range of the transmitter is 11.77 kPa, with a negative offset of 13.25 kPa. 24. According to the principle of hydrostatic pressure, we have P = ρgh; thus, h = P/ρg = 40×10³ / (1000×9.81) = 4.08 m. Therefore, the actual liquid level height H is H = h + h1 = 4.08 + 0.2 = 4.28 m.
25. Under standard conditions, the adjustable ratio is R = Qmax/Qmin = 50 m³/h / 2 m³/h = 25. Hence, at an opening of 1 cm, the flow rate is Q = Qmin × R^(1/L) = 2 m³/h × 25^(1/3) = 5.85 m³/h.
26. 25.4 × 1/8 = 3.175 mm.
27. t = T – 273.15 = 297 – 273.15 = 23.84 (°C).
28. The value of P_table is 9.604 MPa ； Pb=101.7kPa≈0.1MPa. P_abs = P_surface + Pb = 9.604 + 0.1 = 9.704 (MPa). 29. The maximum current Im = √2 × I = √2 × 10 = 14.1 (A). The maximum voltage Um = √2 × U = √2 × 220 = 308 (V). 30. U = IR = 0.05 × 800 = 40 (V). 31. Using the conversion relationship between pressure and units, 1 mmHg = 133.3 Pa; therefore, 765 mmHg = 765 × 133.3 Pa = 101974.5 (Pa). 32. As required, the power of this motor must be sufficient to perform 50 kW•h of work within 5 hours. The formula for calculating power N is N = W/τ, where W represents the work in joules ； τ--time of work, s. Therefore, N=50/5=10(kW). 33. The formula for calculating absolute pressure from gauge pressure is P_abs = P_gauge + P_atm. Given that the gauge pressure is P_gauge = 0.12 Mpa and P_atm = 680 mmHg, then P_abs = 680×133.3 + 0.12×1000000 = 210644(Pa). 34. Since 1 mmH2O ≈ 9.81 Pa, then 10 mmH2O = 10×9.81 = 98.1(Pa). 35. Since 1 L = 10^-3 m3, then 40 L = 40×10^-3 = 0.04(m3). 1. A differential pressure gauge has a maximum differential pressure of 1600 mmH2O and a precision class of 1. What is the maximum allowable error for this gauge? If the calibration point is at 800 mmH2O, what is the allowable range of variation for the differential pressure at that point? (1 mmH2O ≈ 10 Pa). 2. There is a measuring instrument with a precision class of 0.5 and a range of 0–1000°C. Under normal conditions, its maximum absolute error is 6°C. Determine ① the maximum permissible error for this instrument ； ②Basic error ； ①allowable error ； ④Is the accuracy of the instrument satisfactory? 3. There is a pressure gauge with an accuracy class of 2.5 and a measurement range of 0–100 kPa; what is the smallest division on its scale? 4. When calibrating a pressure transmitter with a measurement range of 20–1000 kPa, only a standard gauge with a range of 0–600 kPa and an accuracy class of 0.35 is available. Can this gauge be used as a standard reference gauge?
5. A gauge indicates a gauge pressure of 150 kPa, with the local atmospheric pressure being 1000 kPa. What value will an absolute pressure gauge read in this case?
6. A pressure gauge installed 5 meters below a boiler shows a reading of 500 kPa for the pressure in the boiler’s gas phase. What is the actual pressure in the boiler’s gas phase? (γ = 10,000 N/m³)
7. An absolute pressure transmitter has a measurement range of -100–500 kPa. Calculate the pressures required to produce output values of 4 mA, 8 mA, 12 mA, 16 mA, and 20 mA respectively. What is the output when the transmitter is powered on but no pressure signal is applied? (Local atmospheric pressure = 1000 kPa)
8. The level of liquid in an open container is measured using a U-tube manometer. The density of the liquid is ρ1 = 1.2 g/cm³, and the height of the liquid column in the U-tube is 500 mm. The density of the fluid in the U-tube is ρ2 = 1.5 g/cm³. What is the height h of the liquid level in the container? (See figure below.)
9. As shown in the figure, the range of the liquid level being measured is H = 3000 mm, and the density of the liquid is ρ = 1.2 g/cm³. Calculate the pressure measurement range of the transmitter.
10. A single-flange level gauge is used to measure the level in an open container. The distances from the highest and lowest liquid levels to the gauge are hl = 3 m and h2 = 1 m, respectively. If the density of the liquid is ρ = 1 g/cm³, what are the gauge’s measurement range and zero point shift?
11. A double-flange transmitter is used to measure the level in a closed container. The zero point and measurement range of the transmitter have been calibrated. However, due to maintenance needs, the transmitter’s installation position is lowered by a distance of h2 = 0.5 m, as shown in the figure. Given that h = 5 m, hl = 1 m, the density of the fluid in the container is ρ1 = 1.0 g/cm³, and the density of the oil filling the transmitter’s capillary tube is ρ2 = 0.8 g/cm³, how will the zero point and measurement range of the transmitter change after it is lowered? 12. It is known that the length of the float for a measuring level is L = 600 mm. The density of the heavy medium to be measured is ρ2 = 1.25 g/cm3, while the density of the light medium is ρl = 0.8 g/cm3. When using water as a reference for calibration, how high should the water level be at the zero point and within the measurement range? (The density of water is taken as 1.0 g/cm3.) 13. Determine the transfer function of the system shown in the diagram, and calculate its dynamic parameters. 14. In a ratio control system, the range of transmitter G1 is 0–8000 m3/h, while the range of transmitter G2 is 0–10000 m3/h. After taking the square root of the flow rate, a pneumatic ratio controller or a pneumatic multiplier is used. If G2/G1 = K = 1.2 is to be maintained, what values should be set for the ratio coefficients in the controller and the multiplier? 15. If the flow coefficient C of the control valve is 50, and the pressure difference across the valve is 16×100 kPa with a fluid density of 0.81 g/cm3, what is the maximum flow rate that can pass through? 16. A temporary oil tank has a volume of 8.1 m3. An oil filter with a flow rate of 150 L/min is used to fill this tank. How long will it take to fill the tank? 17. There is a pressure gauge with a range of 0–25 MPa and an accuracy class of 1. During verification, at 20 MPa, the reading was 19.85 when rising and 20.12 when falling; calculate the variation of this gauge. Is this form valid? 18. A pressure gauge is installed 10 meters vertically above the bottom of a water tank, and its reading is 1.9. What is the pressure at the bottom of the tank? (Find the gauge pressure at the bottom.) 19. To thread an M24×2 screw, the required thread depth is 40 mm; determine the drilling depth needed. 20. Use the formula to calculate the diameter of the round rod before threading it with the following thread sleeve. (1)M24 ； (2)M30。 21. Use a Φ6 round steel bar to bend into a ring with an outer diameter of 200 mm; determine the cutting length of the steel bar. 22. To manufacture a circular tube with an outer diameter of 100 mm and a height of 50 mm, formed by bending and welding 5 mm thick steel plates, calculate its blanking dimensions. 1. The maximum allowable error of the instrument is 1600×1% = 16 mmH2O. At a calibration point of 800 mmH2O, the allowable range of differential pressure is (800 ± 16) mmH2O; in other words, the differential pressure can vary within the range of 784–816 mmH2O. 2. ① The maximum permissible error δ = ×100% = 0.6% ； ②Basic error = 0.6% ； ③Allowable error = ±0.5% ； ④The accuracy of the instrument is not satisfactory, as its basic error is 0.6%, which is greater than the allowable error of ±0.5% for this instrument. 3. The maximum absolute error of this instrument is Δmax = 2.5% × (100 – 0) = 2.5 kPa. Since the division values on the instrument’s scale should not be smaller than the absolute error corresponding to its allowable error, the scale can have at most (100 – 0) / 2.5 = 40 divisions. 4. The output pressure range of the pressure transmitter is 20–1000 kPa, with a maximum allowable absolute error of ±80×1% = ±0.8 kPa. When using a standard pressure gauge of O~600 kPa, its maximum allowable error is ±600×0.35% = ±2.1 kPa. It can be seen that the error of the calibration table is greater than that of the instrument being calibrated; therefore, it cannot be used as a standard output table. In calibration work, the allowable error for a standard table should generally be one-third of the allowable error for the instrument being calibrated. 5. P_abs = P_table + P_large = 150 + 100 = 250 kPa. 6. When the instrument is installed 5 meters below the boiler, this introduces an error equivalent to a water column height of 5 meters; thus, the actual pressure is P = P_side – P_influence = 500 – Hγ = 500 – 5×10000/1000 = 450 kPa. 7. The measurement range of the instrument is from -100 to 500 kPa; hence, its full scale range is 500–600 kPa. Assuming that when the input pressure is P_abs, the transmitter outputs the corresponding current value, then: (P_abs/600)×16 + 4 = 4, so P_abs1 = 0 kPa; (P_abs2/600)×16 + 4 = 8, so P_abs2 = 0 kPa; (P_abs3/600)×16 + 4 = 12, so P_abs3 = 0 kPa; (P_abs4/600)×16 + 4 = 16, so P_abs4 = 0 kPa; (P_abs5/600)×16 + 4 = 20, so P_abs5 = 0 kPa. Even in the absence of an input pressure, the transmitter still experiences a pressure of 1 atmosphere, so the output current is J = (100/600)×16 + 4 = 6.67 mA. 8. The pressure generated by the U-tube is P′ = ρ2gh′. The pressure generated when the liquid level in the container is at height h is P = ρ1gh. When P′ = P, then ρ2gh′ = ρ1gh, and thus h = ρ2h′/ρ1 = 1.5×500/1.2 = 625 mm. 9. When there are minor bubbles escaping from the lower end of the air duct, the air pressure inside the duct is almost equal to the static pressure generated by the liquid level, i.e., P = ρgH = 1.2×9.8×3 = 35.28 kPa. Therefore, the pressure measurement range of the transmitter is from 0 to 35.28 kPa. 10. As can be seen from the diagram, the effective measurement range of the instrument is h1 – h2 = 2 m. Therefore, the range of the instrument Δp is given by ΔP = (h1 – h2)ρg = (3 – 1) × 1 × 9.8 = 19.62 kPa. When the liquid level is at its lowest, the pressures acting on the positive and negative chambers of the instrument are respectively P+ = ρg h2 = 1 × 9.81 × 1 = 9.81 kPa, and P- = 0. Thus, the displacement of the gauge is P+ – P- = 9.81 – 0 = 9.81 kPa (positive displacement).

11. Before the installation position of the instrument was lowered, its range was ΔP1 = ρ2gh = 1 × 9.81 × 5 = 49.05 kPa. The displacement A1 was calculated as A1 = ρ2gh1 – ρ2g(h1 + h) = –ρ2gh = –0.8 × 9.81 × 5 = -39.24 kPa. Hence, the adjusted range of the instrument is -39.24 to 9.81 kPa. After the instrument is installed at a lower position, its range becomes ΔP2=ρ1gh=l×9.81×5=49.05 kPa. The displacement A2 is given by A2=ρ2g (h1+ h2)–ρ2g (h1+ h2+h)=–ρ2gh=–0.8×9.81×5=–39.24 kPa. The calibration range of the instrument is -39.24 to 9.81 KPa; in other words, when the transmitter is moved downward, its zero point and range remain unchanged. At the lowest level, the instrument reads zero, as the float is completely submerged in the light medium. Therefore, for water calibration, it should be AL_waterρ_water = AL_ρ1 → L_water = L_ρ1/ρ_water = 600×0.8/1 = 480 mm. At the highest level, the instrument reads full scale, as the float is completely submerged in the heavy medium. Thus, for water calibration, it should be AL_waterρ_water = AL_ρ2 → L'_water = L_ρ2/ρ_water = 600×1.25/1 = 750 mm. Clearly, this height exceeds the length of the float; therefore, a correction must be made during calibration. Based on the calculations above, the range of variation in water level is ΔL_water = 750 – 480 = 270 mm. During calibration, the zero point needs to be adjusted to 600 – 270 = 330 mm; thus, the water level at the full scale point will be 600 mm. After calibration, the zero point must be adjusted back to its original position before the device can be used again. 13. The system consists of a proportional plus integral plus first-order inertia element, and its transfer function can be expressed as G(s) = K/s(Ts+1). With a corner frequency of ω = 10, it follows that Tl = 1/10 = 0.1. Since 20lg|G(jω)| = 6, we have 20lgK – 20lgω = 6; therefore, K = 20. Hence, the transfer function is G(s) = 20/s(0.1s+1). 14. ① When a pneumatic ratio controller is used, since the flow rate passes through a differential pressure transmitter and then through a square root converter, the formula for determining the set value is Kˊ=K×G1max/G2max=1.2×8000/10000=0.96. Therefore, the ratio value in the ratio controller should be set to 0.96. ②When using a pneumatic multiplier, the formula for determining the set value is PB=80K×G1max/G2max + 20 = 80×1.2×8000/10000 + 20 = 96.8 kPa; therefore, the set value for the pneumatic multiplier should be 96.8 kPa. 15. Volumetric flow rate Q = C√ΔP/ρ = 50√16/0.81 = 222 m3/h; Mass flow rate Q = C√ΔPρ = 50√16×0.81 = 180 t/h.
16. 8.1 m3 = 8.1×1000 = 8100 L; 8100/150 = 54 minutes.
17. Variation = |20.12 – 19.85| = 0.27 MPa. The allowable error for this gauge is ±25×1% = 0.25 MPa. Since the variation is greater than the allowable error, this gauge is not acceptable.
18. P_bottom = P_gauge + P_liquid_column. Since P_liquid_column = 10 mH2O ≈ 0.1 MPa, then P_bottom = 1.9 + 0.1 = 2.0 MPa.
19. Drilling depth = Required drilling depth + 0.7d (where d is the outer diameter of the thread) = 40 + 0.7×24 = 56.8 mm.
20. (1) D ≈ d – 0.13t (where d is the outer diameter of the thread and t is the pitch) = 24 – 0.13×3 = 23.61 mm. (2) D ≈ d – 0.13t = 30 – 0.13×3.5 = 29.54 mm.
21. The cutting length is calculated based on the diameter of the center of the finished ring. L = (200 – 6) × 3.14 = 194 × 3.14 = 609.16 mm. 22. The material required is calculated based on the center of the tube wall after bending and welding. L = (100 – 5) × 3.14 = 298.3 mm. 1. The pressure of the medium to be measured is 1.0 MPa, and the ambient temperature around the instrument is ta = 55°C. A Bourdon tube pressure gauge is used for measurement, with a required measurement accuracy of δa = 1%. Determine the measurement range Pd and accuracy class δd of this pressure gauge. (The temperature coefficient β is 0.0001.) 2. A single-flange level gauge is used to measure the liquid level in an open container. The gauge has been calibrated, but due to maintenance requirements, its installation position was lowered by a distance ΔH. Calculate how the gauge’s indication will change as a result, and what should be done to address this issue. 3. Explain through derivation how a float level gauge measures the liquid interface, and what are the conditions under which it functions. 4. In industry, the hydraulic pressure at the bottom of storage tanks is often used to calculate the mass of the liquid inside. As shown in the diagram, a pipe is inserted into the tank, and compressed air is sent into this pipe. When bubbles emerge from the liquid surface, the valve is closed to stop the flow of air. The pressure at point B is measured to be 0.16 MPa. If the cross-sectional area of the tank is 500 m² and the distance from the tank bottom to the side walls is 8 m, what is the mass of the liquid in the tank? 5. A float level transmitter is used to measure the water level in a boiler’s drum. Under normal operating conditions, the pressure of saturated steam is 10.00 MPa (absolute pressure), with a density of saturated water of ρW = 688.4 kg/m³ and a density of saturated steam of ρS = 55.6 kg/m³. The length of the float is L = 800 mm. This float transmitter was calibrated using water with a density of ρl = 1000 kg/m³, ignoring the effect of saturated steam (i.e., assuming ρS = 0). Calculate the water level indicated by the gauge when the actual water level in the drum drops to 0% under normal operating conditions. 6. Simplify the block diagram shown in the figure and write down the closed-loop transfer function. 7. Simplify the block diagram of the transfer function shown in the figure and write down the transfer function. 8. Determine the transfer function for the logarithmic amplitude frequency response shown in the figure, and calculate the dynamic parameters. 9. In a certain ratio control system, the range of the primary flow meter transmitter is F1 = 0–1600 m3/h, while the range of the secondary flow meter transmitter is F2 = 0–2000 m3/h ； A differential pressure signal is generated by the orifice plate, and a square-root function is available; the process requirement is F2/F1 = 3. Determine what coefficient the ratio controller should have. 10. In a ratio control system composed of pneumatic unit instruments, the range of the pneumatic ratio controller is 0–4, while the signal range is 0.2–1.0 bar (1 bar = 10^5 Pa). During operation, it was measured that the output signal of the ratio controller was 0.6 bar. What is the ratio coefficient at this time? 11. In a ratio control system using electric type III instruments, the range of the primary flow rate is 0–400 Nm³/h, and that of the secondary flow rate is 0–600 Nm³/h. During operation, the instrument operator measured that the output current of the ratio controller was 12 mA. Assuming the use of a square root function, what is the ratio of the primary to secondary flow rates? (The range of the ratio controller is 0–4.) 12. There are two pneumatic diaphragm control valves, each with an adjustable ratio of R1 = R2 = 50. The maximum flow rate for the first valve is Q1max = 100 m³/h, while that for the second valve is Q2max = 10 m³/h. What is the adjustable ratio when using split-range control? 13. What is the weight of a steel pipe with a diameter of Φ273×10 in kilograms per meter? (Given that the density of steel is ρ = 7800 kg/m³) 1. According to the regulations, if the value to be measured does not exceed 2/3 of the instrument’s range Pd, then 2/3Pd ≥ Pa, which implies Pd ≥ 3/2 Pa = 3/2 × 1.0 = 1.5 MPa. Therefore, the measurement range of the pressure gauge should be set at 0–1.6 MPa. Temperature-induced error: ΔPF = Pdβ(ta – 25) = 1.5 × 0.0001 × (55 – 25) = 0.0045 MPa. Allowable error for the pressure gauge: δd = Required measurement accuracy – Temperature-induced error = 1 × 1% – 0.0045 = 0.0055 MPa. The accuracy of the gauge is (0.0055 / 1.6 – 0) × 100% = 0.34%. Therefore, a pressure gauge with a measurement range of 0–1.6 MPa and an accuracy class of 0.25 should be selected. 2. Assume that the lowest liquid level in the medium is at the center of the flange. When the liquid level is low, the pressure acting on the positive-pressure side of the level gauge is Hρg (where ρ is the density of the liquid filling the capillary of the level gauge). During calibration, this Hρg value must be adjusted upward. However, if after the migration the gauge moves downward by a distance ΔH, then at the lowest liquid level the pressure on the positive-pressure side of the gauge becomes Hρg + ΔHρg; in other words, an additional ΔHρg is present in the positive-pressure chamber. As a result, the output of the level gauge increases. To ensure accurate measurements in this case, it is necessary to migrate ΔHρg in the positive direction as well. 3. Let the weight of the floating ball be G, and its volume be V. The volumes of the floating ball in the two media are V1 and V2 respectively, with the densities of the two media being ρ1 and ρ2. According to the measurement principle of the float level gauge, the weight G of the float equals the sum of the buoyant forces acting on it in the two media at the two interfaces; that is, G = V1ρ1 + V2ρ2. Therefore, V2 = (G – V1ρ1) / ρ2 = (G – Vρ1) / (ρ1 – ρ2). It can be seen from this formula that if ρ1, ρ2, V, and G remain constant, then V2 also remains constant. When the interface changes, the float will change in sync with the interface, thereby causing the level gauge to indicate the actual liquid level in the container. This is possible provided that the weight G of the float, its volume V, and the specific gravities ρ1 and ρ2 of the two media do not change. 4. Since the density of compressed air is higher than that at normal pressure, the pressure resulting from the weight of the air must be taken into account; that is, P2 = P1 + Δρ2gh. Here, Δρ represents the increase in air density due to compression. According to the gas law, Pa/P2 = (Pa + P1) / (P2 + ΔPa), which leads to Δρ2 = P1ρ2/Pa. Here, Pa denotes atmospheric pressure ； ρ2 is the air density. Substituting equation (2) into equation (1) gives P2 = P1 + P1ρ2gh/Pa = P1(1+ρ2gh/Pa). From the tables, ρ2 = 1.2 kg/m3 and Pa = 1.01×10^5 Pa. Therefore, P2 = P1(1+1.2×9.81×8/1.01×10^5) Pa, which implies that P1 = 0.9991 P2. Since P1 = mg/A, it follows that m = P1A/g. Thus, the mass of the liquid in the tank is m = 0.9991×0.16×10^6×500/9.81 = 8147.6 tons. 5. For verification, when the water level is considered to be 100%, the buoyant force F100 = LsρWg. Since ρs is assumed to be 0, the buoyant force at a water level of 0% is F0 = 0. In fact, when the water level is 0%, the buoyant force generated is F0actual = LSρsg. Therefore, when the actual water level is 0%, the value indicated by the gauge for the water level is h = LSρsg / LSρWg = ρs/ρW = 55.6/688.4 = 8.1%. 6. The original diagram becomes the following; the transfer function G(S) = C/R = G1G2/(1 + G2H1 + G1G2). 7. The original diagram is simplified to this form: the transfer function G = C/R = G2/(1 – G1)/(1 – G1 + G1G2). The symbols in the first column remain unchanged, indicating that the system is stable. 8. The system consists of a first-order inertial element plus a proportional element; with a transition frequency of ω=10, the inertial element is 1/(0.1s+1). Therefore, 201gK = 20, and K = 10; thus the transfer function of this system is G(s) = 10/(0.1s + 1) • 9. K’ = K × F1max/F2max = 3 × 1600/2000 = 2.4. 10. ① (0.6 – 0.2)/(1.0 – 0.2) = 0.5; ② K’ = 4 × 0.5 = 2. 11. ① (12 – 4)/(20 – 4) = 0.5; ② 0.5 × 4 = 2.0; ③ 2.0 × 400/600 = 1.3. 12. The minimum flow rate for the first valve is Qlmin = 100/50 = 2 m3/h, while the minimum flow rate for the second valve is Q2min = 10/50 = 0.2 m3/h. Hence, the overall adjustable ratio between the two valves is R = Qlmax/Q2min = 100/0.2 = 500. 13. First, determine the volume of metal per meter of steel pipe, and then multiply it by the density. The metal volume of the tube = Cross-sectional area of the tube × Length. The cross-sectional area of the tube = Area of the outer diameter – Area of the inner diameter. The area of the outer diameter = {D/2}²π = 0.2372/4 × π = 58.50 × 10⁻³ (m²). The area of the inner diameter = {(D – 2δ)/2}²π = (0.237 – 2 × 0.01)²/4 × π = 50.25 × 10⁻³ (m²). Therefore, the cross-sectional area of the tube = 58.5 × 10⁻³ – 50.25 × 10⁻³ = 8.25 × 10⁻³ (m²). The metal volume of the tube = 8.25 × 10⁻³ × 3 = 8.25 × 10⁻³ (m³). The weight per meter of tube is: Volume × Density, that is, 8.25 × 10⁻³ × 7800 = 64.35 (kg). A bridge with an accuracy of 0.5 grade has negative readings on its lower scale, representing 25% of the full range; the allowable absolute error for this instrument is 1°C. Determine the upper and lower limits of this instrument’s measurement range. The range is 1℃/0.005 = 200℃; the lower limit is -(200℃×25%) = -50℃. The scale of this instrument spans from -50℃ to 150℃. 2. A vacuum pressure gauge has a range of –100 to 500 kPa. During calibration, the maximum error occurs at 200 kPa; the readings on the calibration gauge are 194 kPa at the upper limit and 205 kPa at the lower limit. Does this gauge meet the accuracy requirement of class 1.0? The percentage decrease = ×100% = (205–194) / ×100% = 1.83% > 1.0%, so it does not meet the precision requirement of level 1.0. 3. An 1151 absolute pressure transmitter with a measurement range of 0–80 kPa (absolute pressure). For calibration, a standard vacuum gauge with a scale range of 100–0 kPa is used. If the local atmospheric pressure is 98 kPa, what will be the reading indicated by the vacuum gauge when the transmitter outputs 12 mA? When the input pressure to the transmitter is P_abs, and the output current is 12 mA, then P_abs/(80-0) × 16 + 4 = 12, which gives P_abs = 40 KPa. Since P_vacuum = P_atmospheric – P_abs, we have 98 – 40 = 58 KPa. Therefore, the reading of the vacuum gauge is 58 KPa, with the transmitter’s output remaining at 12 mA. 4. Calculate the calibrated range and drift amount of the pressure-type level gauge as shown in the figure below. Given that h1 = 5 m, h2 = 1 m, and ρ = 1.0 g/cm3, it can be determined from the figure that the measurement range of the level gauge is: P = ρgh1 = 1.0 × 9.8 × 5 = 49 KPa; the drift amount A = ρgh2 = 1.0 × 9.8 × 1 = 9.8 KPa. Therefore, the calibrated range of the instrument is 9.8–58.8 KPa. 5. A single-flange level gauge is used to measure the liquid level in an open container. The distances from the highest and lowest liquid levels to the gauge’s installation point are respectively h1 = 3 m and h2 = 1 m, as shown in the figure below. If the density of the liquid being measured is ρ = 1 g/cm3, what are the gauge’s range and zero-point adjustment? As can be seen from the diagram, the effective measurement range of the gauge is h1–h2 = 2 m. Therefore, the gauge’s pressure range ΔP = (h1 – h2)pg = (3 – 1) × 1 × 9.81 = 19.62 KPa. When the liquid level is at its lowest, the pressures in the gauge’s positive and negative chambers are respectively P+ = pg h2 = 1.0 × 9.81 × 1 = 9.81 KPa, and P– = 0. Thus, the displacement of the level gauge is P+ – P– = 9.81 – 0 = 9.81 KPa (positive displacement). 6. A dual-flange transmitter is used to measure the liquid level in a closed container; the zero point and range of the level gauge have been calibrated. However, due to maintenance needs, the installation position of the gauge was moved downward by a distance of h2 = 0.5 m, as shown in the diagram below. Given that h=5m, h1=1m, the density of the medium inside the container is ρ1=1.0g/cm3, and the density of the oil filling the transmitter’s capillary is ρ2=0.8g/cm3, determine how the zero point and range of the transmitter will change before and after it moves downward Before the instrument was installed at a lower position, its measurement range was △P1=ｐ1gh=1.0×9.81×5=49.05 KPa. The displacement amount A1 was calculated as A1=ｐ2gh1 – ｐ2g(h1+h) = -ｐ2gh=-0.8×9.81×5=-39.24 KPa. Therefore, the adjusted measurement range of the instrument is -39.24 to 9.81 KPa. After the instrument is installed at a lower position, its measurement range ΔP2 becomes ΔP2 = p1gh = 1.0 × 9.81 × 5 = 49.05 KPa. The displacement amount A2 is equal to A2 = p2g(h1 + h2) – p2g(h1 + h2 + h) = –p2gh = –0.8 × 9.81 × 5 = –39.24 KPa. Thus, the calibrated range of the instrument is from –39.24 KPa to 9.81 KPa; in other words, after the transmitter is moved to a lower position, its zero point and measurement range remain unchanged. 7. Simplify the block diagram shown below and write the closed-loop transfer function. The transfer function is G(S) = C/R = G1G2/(1 + G2H1 + G1G2). 8. If the flow coefficient C of the control valve is 50, and the pressure difference across the valve is 16×100 kPa with a fluid density of 0.81 g/cm3, what is the maximum flow rate that can pass through? Volumetric flow rate, mass flow rate. 9. There are two pneumatic diaphragm sleeve control valves, with an adjustable ratio of R1=R2=50. The maximum flow rate for the first control valve is Qmax=100 m3/h, while that for the second control valve is Q2max=10 m3/h. What is the adjustable ratio when using split-range control? Q1min=100/500=20m3/h ； Q2min=100/500=20m3/h ； R=Q1max/Q2min=100/0.2=500 10. The control system for a certain tower is shown in the figure below; please draw the block diagram of this control system. The block diagram of its control system is as follows: 1. Draw the symbols for AND gates, OR gates, and RS flip-flops, and list the truth tables showing how their outputs change with the inputs (the inputs are IN1 and IN2, while the output is Q). IN1 IN2 Q IN1 IN2 Q R=IN1 S=IN2 Q 0 0 0 0 0 0 0 0 Stay at 0 1 0 0 1 1 0 1 1 1 0 0 1 0 1 1 0 0 1 1 1 1 1 1 1 1 Uncertain 2. Draw a 3-to-2 logic diagram with an unlock switch. in1 OR AND bypass1 in2 OR AND OR bypass2 in3 OR AND bypass3 3. Draw a schematic diagram of the structure of a two-chamber equilibrium container. Solution: Q = S * U = R2 × 5 × 3600 = d2 × 5 × 3600 = (159 – 5 × 2)2 × 5 × 3600 = 314 m3/h. 10. The measurement range of the differential pressure transmitter used in conjunction with the throttling device is 0–40 kPa; the scale of the secondary meter ranges from 0–30 t/h. The value obtained from the secondary meter is taken to the square root, with a 2% reduction for low signal levels. ①If the secondary gauge indicates 10 t/h, what is the input differential pressure of the transmitter? What is the output current of the transmitter? ② If the input differential pressure is 0.01 kPa, what will be displayed on the secondary gauge? Solution: ① Using the formula, △P_real = 2 × △P_measured = 2 × 40 = 4.44 KPa; I = (2 / 16) + 4 = 0.125 + 4 = 5.78 mA. ② Using the same formula, Q_real/Q_measured = SQRT(0.01/40) < 2%. Since the cutoff point for low signals is 2%, the secondary gauge will display 0. 1. There is a measuring instrument with an accuracy class of 0.5 and a range of 0–1000℃. When calibration is carried out under normal conditions, the maximum absolute error is 6°C; determine the 1st and maximum reference errors of this instrument ； 2. Basic error ； 3. Allowable error ； 4. Whether the accuracy of the instrument is satisfactory. Solution: 1. Maximum allowable error δ = ×100% = 0.6%. 2. Basic error = 0.6%. 3. Permissible error = ±0.5%. 4. The instrument’s accuracy does not meet the requirements. Because the basic error of this gauge is 0.6%, which is greater than the allowable error of ±0.5% specified for the instrument. 2. There is a pneumatic differential pressure transmitter with a measurement range of 25,000 Pa; the corresponding maximum flow rate is 50 t/h. The process requirement is that an alarm be triggered at a flow rate of 40 t/h. Question: (1) What should the alarm value be set at without a square root calculator? (2) When a square root calculator is used, what should the alarm value be set at? Solution: 1. Without a square root function, the differential pressure corresponding to a flow rate of 40 t/h is ΔP1 = 25000 × (40/50)² = 16000 Pa. The output voltage corresponding to this flow rate is P_out1 = (16000/25000) × 80 + 20 = 71.2 KPa. Therefore, the alarm value S is 71.2 KPa. 2. With a square root function, since ΔQ = K × ΔP, the differential pressure corresponding to a flow rate of 40 t/h is ΔP2 = 25000 × (40/50) = 20000 Pa. The output voltage corresponding to this flow rate is P_out2 = (20000/25000) × 80 + 20 = 84 KPa. Hence, the alarm value S is 84 KPa. 3. The mass flow rate of the superheated steam is 100 t/h, and the inner diameter of the pipe used is D = 200 mm. If the density of the steam is ρ=38 kg/m3, what is the average flow velocity of the steam in the pipe? Solution: The relationship between mass flow rate M and volume flow rate Q is given by: Q = M/ρ = 100×1000/38 = 2631 m3/h = 0.731 m3/s. The cross-sectional area of the pipe, S, is S = (π/4)D2 = (π/4)×(0.2)2 = 0.0314 m2. Since Q = S×u, the average flow velocity of the steam, u, is u = Q/S = 0.731/0.0314 = 23.3 m/s. 4. The original measurement range of the 1151GP pressure transmitter was 0–100 KPa; now its zero point has shifted by 100%. Then 1. What becomes the measurement range of the instrument? 2. What is the range of the instrument? 3. At what pressure values will the instrument output 4, 12, and 20 mA? Solution: The original measurement range of the instrument was 0–100 KPa; now the zero point has shifted upward by 100%. Therefore: 1. The measurement range has become 100–200 KPa. 2. The range of the gauge is 200–100 = 100 KPa. 3. When the input is 100 KPa, the instrument’s output is 4 mA. When the input is 150 KPa, the instrument's output is 12 mA. When the input is 200 KPa, the instrument's output is 20 mA. 5. Convert the following process flow diagram into a system block diagram. Answer: 6. There is a differential pressure gauge used to measure the liquid level in a tank. Given that H = 5 m, h0 = 1.2 m, and H0 = 7.2 m, determine: 1. The amount of migration, and indicate whether it is positive or negative migration ； 2. What is the range of this transmitter? (Assume the liquid level density ρ = 0.96 g/cm3) Solution: When the liquid level is at zero, P0 = ρg(h0 – H0) = -56.448 kPa, indicating negative migration. At full liquid level, P = ρg(H + h0 – H0) = -9.408 kPa. The range of values is: -56.448 kPa to -9.408 kPa. 7. For a certain throttling device steam flow meter, the originally designed steam pressure is 2.94 MPa and the temperature is 400°C. In actual use, the steam pressure at the measured point is 2.84 MPa (with constant temperature). When the flow meter indicates 102 t/h, what is the actual flow rate in tons per hour? (Vapor density table: at 2.94 MPa and 400°C, ρ = 9.8668 kg/m3) ； At 2.84 MPa and 400°C, ρ = 9.5238 kg/m3). Solution: Actual M = Design M × SQRT(Actual ρ / Design ρ) = 102 t/h × SQRT(9.5238 / 9.8668) = 102 t/h × 0.9825 = 100.2 t/h. Therefore, the actual flow rate is 100.2 t/h. 8. A single-tube mercury manometer is currently being used to measure the pressure inside a certain air tank. If the local gravitational acceleration is the standard value (i.e., g=980.665 cm/s2) and the local ambient temperature is 30°C, with a gauge pressure reading of 420 mmHg on the pressure gauge, what is the absolute pressure inside the tank in mmHg, and what is its equivalent in Pa? (The atmospheric pressure at standard gravity is 760 mmHg; the densities of mercury at 0°C and 30°C are 13.5951 and 13.52 g/cm3, respectively.) Solution: The absolute pressure inside the tank is P_abs = P_atmospheric + P_gauge = 760 + 420 × (13.52/13.5951) = 760 + 417.68 = 1177.68 mmHg. 1177.68 mmHg = 1177.68 × 13.5951 × 9.80665 = 157.011 KPa. The absolute pressure inside the tank is 1177.68 mmHg, which is approximately equal to 157.011 KPa. 9. Flow rate is measured using a differential pressure transmitter; the differential pressure is 25 Kpa, the range of the secondary meter is 0–200 T/h, and the output current of the differential pressure transmitter is 4–20 mA. Determine the corresponding differential pressure values and current values when the flow rate is 80 T/h and 100 T/h Solution: According to the differential pressure flow formula: F2 = K × Δp. Δp_x/Δp = (Fmax/F)². Therefore, Δp_x = Δp × (Fmax/F)² = 2500 × (80/200)² = 4000 Pa. I = (Fmax/F) × 16 + 4 = 6.56 mA. Δp_x = 2500 × (100/200)² = 6250 Pa. I = (100/200)² × 16 + 4 = 8 mA. 10. It is given that in a 24VDC power supply circuit, there are 2 12V, 1.5W indicator lights and 1 12V, 1.5W indicator light in series. What is the actual power of each light bulb? Solution: (1) The resistance of each bulb is as follows: For 12V, 1.5W: 12×12/1.5 = 96 ohms; for 12V, 1W: 12×12/1 = 144 ohms. (2) The resistance of the series circuit is: 96×2 + 144 = 336 ohms. (3) The current in the series circuit is: 24/336 = 0.0714 A. (4) The power of each indicator light is as follows: For 12V, 1.5W: 0.07142×96 = 0.49 W; for 12V, 1W: 0.07142×144 = 0.724 W. Therefore, after connecting them in series, the power of each 12V, 1.5W indicator light is 0.49 W ； The power of the 12V, 1 W indicator light is 0.74 W. 11. Complete the timing diagram based on the following PLC ladder diagram: Ladder diagram: Timing diagram: 　　　　　　　　　10S Solution: 1) If the internal resistance of an electrical appliance is 24 ohms, the supply voltage is 60V, and the internal resistance of the power supply is 1 ohm, what is the current flowing through the electrical appliance? Solution: I=U/R = 60/(24+1) = 2.4A. 2) The original measurement range of the 1151GP pressure transmitter was 0–100 KPa; now the zero point has shifted by 100%. Then 1. What becomes the measurement range of the instrument? 2. What is the range of the instrument? 3. At what pressure values will the instrument output 4, 12, and 20 mA? Solution: The original measurement range of the instrument was 0–100 KPa; now the zero point has shifted upward by 100%. Therefore: 1. The measurement range has become 100–200 KPa. 2. The range of the gauge is 200–100 = 100 KPa. 3. When the input is 100 KPa, the instrument’s output is 4 mA. When the input is 150 KPa, the instrument's output is 12 mA. When the input is 200 KPa, the instrument's output is 20 mA. 3) There are two temperature measuring instruments, with measurement ranges of 0–800°C and 600–1100°C respectively. It is known that their maximum absolute error is ±6°C for each. Determine their accuracy grades respectively. Solution: Using the basic error formula δm = Δmax/(A_upper – A_lower) × 100%, we get δm1 = 6/(800 – 0) × 100% = 0.75%, and δm2 = 6/(1100 – 600) × 100% = 1.2%. According to the accuracy class standards for common industrial instruments, temperature measuring instruments with a measurement range of 0–800°C should have an accuracy class of 1, while those with a measurement range of 600–1100°C should have an accuracy class of 1.5. 4) There is a pneumatic differential pressure transmitter with a measurement range of 25,000 Pa; the corresponding maximum flow rate is 50 t/h. The process requirement is that an alarm be triggered at a flow rate of 40 t/h. Question: (1) What should the alarm value be set at without a square root calculator? (2) When a square root calculator is used, what should the alarm value be set at? Solution: 1. Without a square root function, the differential pressure corresponding to a flow rate of 40 t/h is ΔP1 = 25000 × (40/50)² = 16000 Pa. The output corresponding to this flow rate is P_out1 = (16000/25000) × 80 + 20 = 71.2 KPa. Therefore, the alarm value S is 71.2 KPa. 2. With a square root function, since ΔQ = K × ΔP, the differential pressure corresponding to a flow rate of 40 t/h is ΔP2 = 25000 × (40/50) = 20000 Pa. The output corresponding to this flow rate is P_out2 = (20000/25000) × 80 + 20 = 84 KPa. Hence, the alarm value S is 84 KPa. 5) When a certain throttling device was designed, the density of the fluid was 520 Kg/m³; however, in actual use, the density is 480 Kg/m³. If, during design, the differential pressure transmitter outputs 100 KPa corresponding to a flow rate of 50 t/h, what will be the corresponding flow rate in actual use? Solution: Using the basic formula based on mass flow rate, and since all conditions other than the fluid density remain unchanged, with the designed fluid density ρ_design = 520 Kg/m³ and the actual fluid density ρ_actual = 480 Kg/m³, and the designed flow rate when the transmitter outputs 100 KPa being M_design = 50 t/h, then the actual flow rate M_actual is… 6) While calibrating an 1151AP absolute pressure transmitter, it was found that as long as power was supplied, the instrument would output 12 mA. Is this phenomenon normal? (If the measurement range of the gauge is 50–150 KPa gauge pressure, and the atmospheric pressure at that time is 100 KPa) Solution: An absolute pressure transmitter measures absolute pressure; its measurement range is 50–150 KPa. In other words, when an input of 50 KPa gauge pressure is applied, the transmitter outputs 4 mA ； When an absolute pressure of 150 KPa is applied, the instrument outputs 20 mA ； At atmospheric pressure, that is, when an input pressure of 100 Kpa is applied, the instrument’s output is ×(100-50)+4=12mA. The instrument’s output is currently exactly 12mA, so it is functioning normally. 7) There is a differential pressure transmitter with a measurement range of 0–10000 Pa. The manual for this instrument specifies that a negative drift of 100% is possible (the maximum drift amount being -100%). What is the maximum drift amount for this instrument? Solution: Negative migration refers to shifting the zero point in the negative direction without changing the range; the percentage of this shift relative to the range is the percentage of migration. Migration amount = 10000 × 100% = 10000 Pa; therefore, a transmitter operating in the 0–10000 Pa range can be migrated to the -10000–0 Pa range. 8) When the detection system of the nickel-chromium/nickel-silicon thermocouple is in operation, the temperature at its cold end is t0 = 30°C. The instrument measures the thermoelectromotive force E(t, t0) = 39.17 mV. Determine the actual temperature of the medium being measured. Solution: Using the table, we find that E(30º, 0º) = 39.17 mV. Moreover, E(t, 0º) = E(t, 30º) + E(30º, 0º) = 39.17 + 1.2 = 40.37 mV. From the table, the corresponding value for 977°C is also obtained. 9) When using a differential pressure transmitter to measure flow rate, the differential pressure is 25 KPa; the range of the secondary meter is 0–200 T/h, and the output current of the differential pressure transmitter is 4–20 mA. What are the corresponding differential pressure values and current values when the flow rate is 80 T/h and 100 T/h? Solution: According to the differential pressure flow formula: F2 = K × Δp. Δp/x/Δp = (Fmax/F)², so Δp = Δp × (Fmax/F)² = 2500 × (80/200)² = 4000 Pa. I = (Fmax/F) × 16 + 4 = 6.56 mA. Δp = 2500 × (100/200)² = 6250; I = (100/200)² × 16 + 4 = 8 mA. 10) When using a differential pressure transmitter to measure flow, the differential pressure is 25 KPa. The range of the secondary meter is 0–200 T/h, and the counter advances 1000 counts per hour at full scale. The output current of the differential pressure transmitter is 4–20 mA. Determine the number of counts per hour when the flow rate is 80 T/h and 100 T/h, as well as the current value represented by each count. Solution: Let the number of counts be X. 1) For a flow rate of 80 T/h: 80/200 = X/1000 → X = 80 × 1000/200 = 400 counts/hour. 2) For a flow rate of 100 T/h: 80/200 = X/1000 → X = 80 × 1000/200 = 500 counts/hour. 3) The flow rate represented by each count is 200 T/h / 1000 counts/h = 0.2 T per count. 11) If the control valve is fully open, the pressure difference before and after the valve is 400 KPa, and the flow rate of clean water is 100 m³ per hour. What is the flow coefficient C of the valve, and what is its CV value? Solution: Given that Q = 100 m3/h, ΔP = 400 KPa, r = 1 gf/cm3, Cv = 1.17, and C = 1.17 × 50 = 58.5. 12) Use a glass U-tube to measure the vacuum level at PA in container B. The installation diagram is as follows. From the diagram, it can be seen that the vacuum level at PA is 380 mmHg, while the external atmospheric pressure is 760 mmHg. What is the absolute pressure at PA? Solution: P_abs = P_surface + P_atmosphere. P_surface = -380 mmHg = -50.67 KPa; P_atmosphere = 760 mmHg = 101.33 KPa. Therefore, P_abs = -50.67 KPa + 101.33 KPa = 50.66 KPa. The absolute pressure at PA is 50.66 KPa. 13) For a throttling device used as a steam flow meter, the designed steam pressure is 2.94 MPa and the temperature is 400°C. In actual use, the steam pressure at the measured point is 2.84 MPa (with constant temperature). When the flow meter indicates 102 t/h, what is the actual flow rate? Water vapor density table: at 2.94 MPa and 400°C, ρ = 9.8668 kg/m3 ； At 2.84 MPa and 400°C, ρ = 9.5238 kg/m3; the actual flow rate is 100.2 t/h. 14) A metal wire with a length of 200 M and a cross-sectional area of 0.20 cm2 has a resistance of 10 ohms. Determine its mechanical properties Solution: According to Ohm’s law, R = ρt/s. Since ρ = Rs/t = 10 × 0.00002/200 = 0.000001 (Ωm), the electrical conductivity of the metal is 1.0×10-6 ohm-meters. 15) Calculate the total resistance within a junction box containing three devices connected in parallel. Solution: Let the internal resistance of each instrument box be r, and the total internal resistance of the parallel-connected instrument boxes be R. According to the rules for resistors in parallel, 1/R = 1/r1 + 1/r2 + 1/r3. Therefore, 1/R = 3/r, and thus R = r/3. 16) Given that the power supply for the instruments is 24 V and the output power is 32 W, determine the output current. Solution: P=UI; I=P/U. Therefore, I=32 W/24 V=1.33 A. 17) When using a WZG-type thermistor for temperature measurement, its resistance value is 71.02 ohms. If R0=53 ohms and A=4.25×10^-31 per degree, what is the temperature in degrees Celsius? Solution: Rt = R0(1 + At). t = (Rt – R0) / (R0A). t = (71.02 – 53) / 53 × 4.25 × 10^-3. t = 80°C. 18) A platinum-rhodium-platinum thermocouple is used to measure the temperature inside a furnace; in the absence of any other compensation methods, the electromotive force measured is 10.638 mV, and the temperature at the free end of the thermocouple is 50°C. Determine the actual temperature. Solution: The value corresponding to 50°C as per the table is 0.299 mV. Therefore, E(t, 0°C) = 10.638 + 0.299 = 10.938 mV. Using the table, the corresponding temperature is t = 1118°C. 19) When using a DDZ-Ⅲ type differential pressure transmitter to measure flow rate, with a flow range of 0–16 m3/h, what is the output signal when the flow rate is 12 m3/h? Solution: The differential pressure is proportional to the square of the flow rate, and the output current of the transmitter is proportional to this differential pressure; therefore, the 4-20mA current output by the transmitter is proportional to the square of the flow rate. That is: (I-4)/(20-4) = Q22/Q12 = 122/162; therefore, I = 4 + 122 = 13 mA. Answer: The output signal is 13 mA. 20) It is known that a 24VDC power supply unit is used to power several 12V indicator lights in series. If the indicator lights are to function properly, how many such indicator lights can be connected in series? If each indicator light has a resistance of 5 ohms, what is the current flowing through each one? Solution: In series, the voltage is divided as 24/12=2; therefore, 2 lamps can be connected in series. The current is I=U/R=24/(5×2)=2.4 A. The current flowing through each indicator lamp is 2.4 A. 21) It is given that a container has a cylindrical shape, with a base area of 4.0 square meters. When it is completely filled with water, its height is 35 meters. What is the pressure at the base area? Solution: F = ρghS = 1000 × 35 × 4 = 140,000 Kg. Answer: The pressure on the base area is 140,000 Kg. 22) A pressure gauge with a grade of 1.5 and a scale range of 0–100 KPa was tested; it was found that the error at 50 KPa was the greatest, at 1.4 KPa, while the errors at other points on the scale were all less than 1.4 KPa. Is this pressure gauge qualified? Solution: The maximum reading error of this gauge = ×100% = 1.4% of P_, so the gauge exhibits positive drift. 3. When the liquid level h is 2.5 m, the output of the instrument is given by I = (h – h2) / (h1 – h2) × (20 – 4) + 4 = (2.5 – 1) / (3 – 1) × 16 + 4 = 16 mA. Figure 39 shows the use of a differential pressure transmitter to measure the liquid level in a closed container. It is known that h2 = 200 cm, h3 = 140 cm, and the density of the liquid being measured is 0.85 g/cm3. Find the transmitter’s range and offset. Solution: ΔP = h2ρg = 200×0.85×980.7×(100/1000) = 16671.9 Pa. At the lowest liquid level, P+ = h3ρg = 140×0.85×980.7×(100/1000) = 11670.3 Pa; P_ = 0. Since P+ > P_, the gauge shows a positive drift. The migration amount is 11670.3 Pa, and the range is 16671.9 Pa. 40) As shown in the figure, the boiler bubble level is measured using a two-chamber equilibrium vessel. Given that P1 = 3.82 MPa, ρ_vap = 19.7 Kg/m3, ρ_liquid = 800.4 Kg/m3, ρ_cold = 915.8 Kg/m3, h1 = 0.6 m, and h2 = 1.5 m, determine the range and zero shift of the differential pressure transmitter. Solution: The range of the differential pressure level gauge is ΔP = h1(ρ_liquid – ρ_vapor)g = 0.6×(800.4 – 19.7)×9.807 = 4593.8 Pa. When the liquid level is at its lowest, the forces acting on the positive and negative chambers of the gauge are as follows: P+ = P1 + h1ρ_vapor×g + h2ρ_water×g = 3.82×10^6 + 0.6×19.6×9.807 + h2ρ_water×g = 3820115.3 + h2ρ_water×g; P_- = ρ1 + h1ρ_cold×g + h2ρ_water×g = 3.82×10^6 + 0.6×915.8×9.807 + h2ρ_water×g = 3825388.8 + h2ρ_water×g. Thus, the drift amount of the gauge is P = P+ – P_- = -5273.5 Pa. Since P+ < P_, there is negative drift. The measurement range of the gauge is from -5273.5 to (-5273.5 + 4593.8) = 679.7 Pa