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True or False Question 1. A control valve consists of an actuator and a valve body component. Answer: √ 2. Pneumatic piston actuators are divided into proportional and two-position types. Answer: √ 3. Electric actuators are divided into straight-stroke and angular-stroke types. Answer: √ 4. The V-type ball valve, also known as a V-notch ball valve, features a ball core that is 1/4 sphere in shape and equipped with a V-shaped notch; its flow capacity is more than twice that of ordinary valves. Answer: √ 5. A self-acting control valve, also known as a directly acting control valve, is a type of control valve that does not require any external energy source; it integrates the functions of measurement, regulation, and actuation into one unit, and uses the energy from the process being controlled to drive its operation. Answer: √ 6. The operating temperature for graphite fillers is -200~600°C, while that for PTFE fillers is -40~250°C. Answer: √7. The ratio of the maximum flow rate to the minimum flow rate that a control valve can regulate is known as the regulation ratio of the control valve. Answer: √ 8. When the pressure difference across the valve remains constant, the flow ratio is known as the ideal adjustable ratio. Answer: √ 9. In actual use, the pressure difference across the valve changes, and the flow ratio under such conditions is referred to as the actual adjustable ratio. Answer: √ 10. The ideal regulation ratio of a valve depends on the structure of its valve core. Answer: √ 11. The actual adjustable ratio of a valve depends on the structure of its valve core and the conditions of the piping. Answer: √ 12. The relationship between the relative flow rate of the medium passing through the valve and the relative stroke of the valve is known as the flow characteristic of the control valve. Answer: √ 13. When the pressure difference across the valve remains constant, it is referred to as an ideal flow characteristic. Answer: √ 14. In actual use, the pressure difference across the valve changes, and the relationship mentioned above is then referred to as the actual flow characteristic. Answer: √ 15. The ideal flow characteristic depends on the valve core structure. Answer: √ 16. The actual flow characteristics depend on the valve core structure and piping conditions. Answer: √ 17. Several flow characteristics of control valves: fast-opening characteristic, logarithmic characteristic, linear, equal percentage, parabolic. Answer: √ 18. The weights of a certain piston pressure gauge are missing, and it is not possible to use the weights from another piston pressure gauge as a substitute. Answer: √ 19. In a pipe, the fluid velocity is generally highest at the centerline of the pipe, and it is zero at the pipe walls. Answer: √ 20. When the Reynolds number is less than 2300, the fluid flow is laminar; when the Reynolds number is greater than 40000, the fluid flow is turbulent. Answer: √ 21. If the Reynolds numbers of fluids are the same, their flow patterns are similar. Answer: √ 22. When the fluid filling a pipe passes through a throttling device, the flow jet undergoes local contraction at the throat, which results in an increase in the flow rate and a decrease in the static pressure. Answer: √ 23. The density of a fluid is related to temperature and pressure. For gases, the density decreases as temperature rises and increases as pressure increases; whereas for liquids, the density mainly decreases as temperature rises, with little effect from pressure. Answer: √ 24. A standard throttling device operates under laminar flow conditions of the fluid. Answer: √ 25. Elbow type pressure tapping and flange type pressure tapping are just different methods of taking pressure measurements; the basic structure of a standard orifice plate remains the same. Answer: √ 26. An elliptical gear flow meter does not require straight pipe sections. Answer: √ 27. An increase in the pressure difference between the inlet and outlet of an elliptical gear flow meter leads to an increase in leakage; an increase in the viscosity of the fluid medium results in a decrease in leakage. Answer: √ 28. The instrument constant of the turbine flow transmitter within its measurement range is calibrated using water at normal temperature. Answer: √ 29. When using a float level gauge to measure the liquid level, it is necessary to ensure that the float can move freely within the float chamber; therefore, the vertical installation of such gauges requires strict adherence to certain standards. Answer: × It is sufficient as long as the float does not touch the inner walls of the float chamber. 30. When using a differential pressure transmitter to measure the liquid level, there is no specific requirement regarding the installation height of the transmitter, as long as maintenance is convenient. Answer: × The installation height must not be higher than that of the lower pressure tapping point. 31. When using a thermocouple to measure temperature, if compensating wires are used for the connections, then it is not necessary to consider cold-end compensation for the thermocouple. Answer: × Compensating wires serve as an extension of the thermocouple, but they do not provide cold-end compensation. Answer: √ 32. The temperature measurement range of copper thermal resistors is wider than that of platinum thermal resistors. Answer: × The temperature measurement range of copper thermal resistors is narrower than that of platinum thermal resistors. 33. Volume flow meters must be cleaned regularly when measuring the flow rate of media that may cause blockages. Answer: √ 34. The smaller the proportionality of the regulator, the greater the amplification factor, and the stronger the proportional control effect. Answer: √ 35. The longer the integration time, the weaker the integrating effect. Answer: √ 36. The stroke of the control valve stem is inversely proportional to the magnitude of the input signal to the valve positioner. Answer: × The stroke of the control valve stem is proportional to the magnitude of the input signal to the valve positioner. 37. In automatic control systems, apart from proportional control which can be applied alone, integral control and derivative control cannot be used separately. Answer: √ 38. When measuring resistance with a multimeter, the error that results from not adjusting the zero point repeatedly is called a negligence error. Answer: × When measuring resistance values, the error resulting from not adjusting the zero point repeatedly is a systematic error. 39. The thermoelectromotive forces of thermocouples A and B are independent of the intermediate temperature of materials A and B, and depend only on the temperatures at the cold and hot ends, T1 and T0. Answer: √ 40. A resistance box can be considered a standard resistor with a variable resistance value. Answer: √ 41. Thermal resistance thermometers cannot be used in areas where temperature changes are small. Answer: × Thermal resistance thermometers can be used in areas where temperature changes are small. 42. The sensitivity of a mercury thermometer mainly depends on the purity of the mercury. Answer: × The sensitivity of a mercury thermometer mainly depends on the diameter of the capillary and the volume of the air reservoir. 43. The temperature measurement principle of thermocouples relies on the thermoelectric effect. Answer: √ 44. When there is a temperature difference between the same object or several objects in direct contact, heat is transferred from the hotter part to the colder part; this phenomenon is known as thermal radiation. Answer: × Between the same object or several objects in direct contact, if there is a temperature difference, heat is transferred from the hotter part to the colder part; this phenomenon is known as heat conduction. 45. When using thermocouples for temperature measurement, it is essential to ensure that the type of compensation wire matches that of the thermocouple being used, and that the polarity of the compensation wire is not connected incorrectly. Answer: √ 46. No cold junction temperature compensation is required when using thermocouples for temperature measurement. Answer: × Cold-junction temperature compensation is required when using thermocouples for temperature measurement. 47. A sheathed thermocouple is a solid cable-like assembly formed by combining a thermocouple wire, insulating material, and a metal tube. Answer: √ 48. When multiple resistors are connected in parallel, the total resistance is equal to the sum of the reciprocals of each resistor’s value. Answer: × When multiple resistors are connected in parallel, the reciprocal of the total resistance is equal to the sum of the reciprocals of each individual resistor’s value. 49. Instantaneous flow rate refers to the amount of fluid flowing through a certain cross-section of a pipe. Answer: × Instantaneous flow rate refers to the amount of fluid that passes through a certain cross-section of a pipe per unit of time. 50. If the Reynolds number is the same, the flow of the fluid is similar. Answer: √ 51. The material used for orifice plates used for flow measurement is generally stainless steel or carbon steel. Answer: √ 52. The commonly used standard throttling devices are: orifice plates, nozzles, Venturi tubes, and 1/4 circle nozzles. Answer: × The commonly used standard throttling devices are: orifice plates, nozzles, and Venturi tubes. 53. Elbow-type pressure tapping orifice plates and flange-type pressure tapping orifice plates differ only in the method of pressure tapping; the basic structure of a standard orifice plate remains the same. Answer: √ 54. When using a throttling device to create a pressure difference in order to measure flow rate, it is required that the fluid being measured maintain a stable flow state before and after the throttling device, and that the entire cross-section of the pipe be completely filled with the fluid in question. Answer: √ 55. When using a orifice plate to measure flow rate, the pressure tapping points must be smooth; there should be no burrs or other impurities. Answer: √ 56. When installing an orifice plate, its center does not need to coincide with the center of the pipe. Answer: × When installing an orifice plate, its center must coincide with the center of the pipe. 57. An electromagnetic flowmeter is neither a volumetric flowmeter nor a constant pressure drop flowmeter; it is a velocity-type flowmeter. Answer: √ 58. The speed of fluid flow is directly proportional to the volume flow rate through the pipe cross-section. Answer: × The speed of liquid flow is inversely proportional to the flow rate through the pipe’s cross-section. 59. A differential pressure flow meter measures flow rate by utilizing the pressure difference generated as fluid passes through a throttling element. √ 60. The residual of the proportional control process is proportional to the proportionality gain of the controller. √ 61. Differential adjustment can eliminate residual errors; it adjusts based on the presence of deviation. Answer: × Integral regulation can eliminate residual errors; it operates based on the presence of deviations. 62. An actuator with a positive action indicates that the control valve is of the air-operated type, and this is independent of the valve body installation. Answer: × The fact that the actuator is of positive action does not mean that the control valve is of air-operated type; it also depends on the way the valve body is installed. 63. When the medium to be regulated contains solid suspensions, a control valve with quick-opening characteristics is advisable. Answer: × When the medium being regulated contains solid suspensions, a control valve with linear characteristics is preferable. 64. When tuning the parameters of a cascade control system, the main loop should be tuned first, followed by the secondary loop. Answer: × When tuning the parameters of a cascade control system, the secondary loop should be tuned first, followed by the primary loop. 65. When tuning PID parameters empirically, for flow control systems, the proportional gain is generally between 20% and 60%. Answer: × When tuning PID parameters using empirical methods, for flow rate processes, the proportional gain is generally between 40% and 100%. 66. The basis for determining the positive and negative actions of the regulator in the control system is to achieve positive feedback in the closed-loop circuit. Answer: × The basis for determining the positive and negative actions of a regulator in a control system is to achieve negative feedback in the closed-loop circuit. 67. Using the R×100 setting on a mechanical multimeter, connect the red test lead to one electrode of the transistor, and touch the black test lead to the other two electrodes. If low resistance values are measured in all cases, then the transistor is an NPN type. Answer: × With a mechanical multimeter set to R×100, connect the red test lead to one electrode of the transistor, and use the black test lead to touch the other two electrodes. If low resistance values are measured in all cases, then the transistor is a PNP type. 68. The level of a substance can be measured by converting changes in its level into pressure or pressure difference. Answer: √ 69. Without any migration, the starting point of measurement is zero; if the starting point changes from zero to a positive value, it is called forward migration. Answer: √ 70. A float-type level gauge is designed based on the principle of variable buoyancy, while a bulb-type level gauge is designed based on the principle of constant buoyancy. Answer: × A float-type level gauge is designed based on the principle of constant buoyancy, while a bulb-type level gauge is designed based on the principle of variable buoyancy. 71. A hydrostatic level gauge operates on the principle that as the liquid level changes, the hydrostatic pressure at a certain point on the bottom or side of the container also changes. Answer: √ 72. Since the calibration range of flanged level gauges is independent of their installation height, changing the installation position after the gauge has been calibrated does not affect its output. Answer: √ 73. When calibrating a float level gauge, a plastic tube is used to connect the bottom of the float chamber; the verticality of this plastic tube does not affect the accuracy of the calibration. Answer: √ 74. In a constant buoyancy type level gauge, the float remains always above the medium, and its displacement changes in a 1:1 ratio as the liquid level changes. Answer: √ 75. To enable the float level gauge to measure an accurate and stable liquid level, its sensing element must be protected from direct impact by the material, and it is best to install it in a dead corner of the liquid. Answer: × To enable the float level gauge to measure an accurate and stable liquid level, its sensing element must be protected from direct impact by the material, but it also cannot be installed in dead corners of the liquid. 76. When using a single-flange level gauge to measure the liquid level in an open container, the gauge’s range refers to the increase in pressure on the level gauge as the liquid level rises from its lowest to its highest point. Answer: √ 77. The measurement range of a differential pressure transmitter is equal to the difference between its full-scale range and the offset value. Answer: × The measurement range of a differential pressure transmitter equals the sum of its span range and the offset value. 78. Accuracy refers to the degree of consistency between the measurement result and the actual value; high accuracy implies that both systematic errors and random errors are small. Answer: √ 79. The amount of charge that passes through a wire per unit time is the current intensity. Answer: √ 80. The resistance of a wire is related to its length. Answer: √ 81. The three impulse level control system is generally used to control the level in a distillation tower. Answer: × The three-impulse level control system is generally used to control the liquid level in the boiler drum. 82. Some instruments use direct current, while others use alternating current. (√) 83. FT stands for orifice plate. (╳) FT stands for transmitter. 84. The power of an instrument is the product of the voltage and current it requires. (√) 85. The range of an instrument is the range it can measure. (√) 86. The setpoint of the automatic control system is manually determined based on production requirements. (√) 87. The isolation fluid in the isolation tank is water. (╳) Ethylene glycol, glycerin, etc. 88. The accuracy class of a instrument refers to its error margin. (╳) The accuracy class of a instrument represents the maximum allowable value for its basic error. 89. The accuracy class of an instrument is the maximum allowable value for its basic error. (√) 90. The measurement range of a 1.5-class instrument is (20~100 degrees), so its span is 80 degrees. (√) 91. Temperature transmitters are used to measure the temperature of a medium. (╳) The function of a temperature transmitter is to convert the potential or resistance signals from thermocouples or thermal resistors into standard DC1-5V voltage or DC4-20mA current signals. 92. Use alcohol and glycerin in winter to calibrate float level gauges. (√) 93. Electromagnetic flowmeters cannot be used to measure the flow rate of gaseous media. (√) 94. When the counterweight of the float level gauge is at the top, the actual liquid level is at its highest. (╳) The actual liquid level is at least 95. The common temperature scales are Celsius, Fahrenheit, and Kelvin, namely ℃, ℉, and K. (√) 96. The greater the proportionality of the regulator, the larger the amplification factor and the stronger the proportional control effect. (╳) The greater the proportionality of the regulator, the smaller the amplification factor, and the weaker the proportional control effect. 97. The output of a thermocouple is a 4–20mA signal. (╳) The output of a thermocouple is a thermoelectric potential signal. 98. The signal circuit is generally grounded at the end of the secondary instrument. (√) 99. The shielding layers of shielded cables and wires must be grounded, and the grounding point should be located on the control room side. (√) 100. In automatic control, a PID controller relies on the proportional action to prevent excessive oscillations, on the integral action to eliminate static errors, and on the derivative action to reduce dynamic errors. (√) 101. In a cascade control system, the main loop is a constant-value control system, while the secondary loop is a follow-up system. (√) 102. When a short circuit occurs on the hazardous side, the resistor in the Zener-type safety barrier can serve to limit the energy released. (√) 103. When the output value of a regulator increases as the measured value increases, it is referred to as positive action. (√) 104. To calibrate an intelligent transmitter, it is sufficient to use a handheld communicator to communicate with the transmitter online, allowing the range of the transmitter to be adjusted as desired. (√) 105. Piston pressure gauges are often referred to as standard pressure instruments for laboratories. (√) 106. Flow rate is proportional to the differential pressure. ( ╳ ) The flow rate is proportional to the square root of the pressure difference. 107. When a double-flange transmitter is used to measure liquid levels, its range depends on the installation height of the gauge. ( ╳ ) The measurement range is independent of the installation height of the gauge head. 108. When a differential pressure transmitter is used to measure flow rate, if the negative pressure lead is blocked, the measured value will be above 100%. ( √ ) 109. When measuring the oil-water interface level, if the tank is filled with water, the interface level is 0. (╳) represents 100%. 110. The annular flow cross-section of the rotameter varies, essentially in proportion to the flow rate, but the flow velocity through the annular gap remains relatively constant. (√) Multiple-choice question 1. 1 pascal is the pressure resulting from a force of 1 newton acting on an area of ( ). (A) 1m2 (B) 2m2 (C) 0.01m2 (D) 0.1m2 Answer: A 2. A thermistor is made of metallic materials with which property? (A) One (B) Two (C) Three (D) More than three. Answer: A. 3. Gauge pressure refers to the difference between ( ) and atmospheric pressure. (A) Standard atmospheric pressure (B) Negative pressure (C) Absolute pressure (D) Engineering atmospheric pressure. Answer: C. 4. The minimum reading that a typical Bourdon tube pressure gauge can show must not be lower than （） of its maximum measurement range. (A) 2/3 (B) 1/3 (C) 1/4 (D) 1/2 Answer: B 5. The function of the diaphragm in a pressure transducer’s sensing element is to convert （ ） into a concentrated force. (A) Differential pressure to be measured (B) Pressure signal (C) Pressure of the medium being measured (D) System pressure Answer: C 6. The differential pressure △P measured by a differential pressure flow meter is ( ). (A) Static pressure difference (B) Dynamic pressure difference (C) Total pressure (D) Relative pressure. Answer: A. 7. In the event of a fire involving electrical equipment in instruments, the power supply must be cut off immediately, and the fire should be extinguished using ( ). (A) Sand (B) Foam fire extinguisher (C) Water (D) Carbon dioxide fire extinguisher. Answer: D. 8. What is indicated by the weights on a piston-type pressure gauge? (A) Weight (B) Mass (C) Pressure (D) Volume Answer: C 9. The control principle of a solenoid valve belongs to ( ). (A) Proportional control (B) On-off control (C) Integral control (D) Differential control Answer: B 10. When using a float level gauge to measure the liquid level, if the float falls off, what will be the output signal of the gauge? (A) Minimum (B) Maximum (C) Zero adjustment (D) Unchanged. Answer: B. 11. When adjusting the zero point of a float-type level transmitter on-site, what should be inside the float? (A) Venting (B) Filling with the medium to be measured (C) Filling with water (D) It doesn’t matter whether there is a medium or not. Answer: A. 12. The glass plate level gauge is manufactured based on the principle of ( ). (A) Static pressure (B) Communicating vessels (C) Variable buoyancy (D) Constant buoyancy. Answer: B. 13. Precision is a term that indicates the magnitude of error; the higher the precision, the ( ) the error. (A) Larger (B) It depends on the specific situation (C) Constant (D) Smaller. Answer: D. 14. When measuring voltage, the voltmeter is connected to the circuit being measured in ( ) fashion. (A) Series (B) Parallel (C) Not specified (D) Both series and parallel. Answer: B 15. In automatic control systems, the type of control that can be applied independently is （ ） control. (A) Differentiation (B) Integration (C) Proportionality (D) Integral differentiation Answer: C 16. The working principle of a piston manometer is ( ). (A) Principle of communicating vessels (B) Principle of strain gauges (C) Principle of hydrostatic balance (D) Principle of capacitive measurement Answer: C 17. The correct procedure for shutting down a differential pressure transmitter is ( ). (A) First, close the positive and negative pressure hand valves of the three-valve assembly, open the balance hand valve, and then close the pressure tapping hand valve. (B) First, close the pressure tapping hand valve, then close the positive and negative pressure hand valves of the three-valve assembly, and open the balance valve. (C) First, close the pressure tapping hand valve, then open the balance valve, and close the positive and negative pressure hand valves. (D) First, open the balance valve, then close the positive and negative pressure hand valves, and finally close the pressure tapping hand valve. Answer: A. 18. LNG production involves high-pressure throttling for cooling; to minimize noise, which of the following can be used? (A) Single-seat valve (B) Sleeve valve (C) Butterfly valve (D) Diaphragm valve Answer: B 19. Which of the following control valves is suitable for use in the FC mode (shut off when air supply is stopped)? (A) Emergency air protection for the evaporator (B) Flash line of the LNG storage tank (C) Pressure relief of the molecular sieve dryer (D) Fuel gas line of the reboiler Answer: D 20. When two-position control is used, the output is either 100% or (). (A) 0% (B) 50% (C) 75% (D) 25% Answer: A 21. Control in chemical production processes mostly relies on （ ） control systems. (A) Fixed value (B) Programmed (C) Follow-up (D) Cascade. Answer: A. 22. A double-flange level gauge is used to measure the liquid level in a container, and both the zero point and range of the gauge have been calibrated. If the instrument is installed at a lower position, the level gauge ( ). (A) The zero point decreases, while the range remains unchanged. (B) The zero point increases, while the range remains unchanged. (C) The zero point remains unchanged, but the range increases. (D) Neither the zero point nor the range changes. Answer: D. 23. The measurement range of a float level transmitter is determined by the ( ) of the float. (A) Installation height (B) Buoy volume (C) Length (D) Weight Answer: C 24. For a negative migration differential pressure transmitter, the starting point of measurement when positive migration is applied is ( ). (A) Full-scale point (B) A positive value (C) A negative value (D) Zero. Answer: C. 25. When calibrating measuring instruments, the （ ） point calibration method is commonly used. (A) 2 (B) 3 (C) 5 (D) 10 Answer: C 26. Combustible gas detectors cannot be used to measure the concentration of (). (A) Oxygen (B) Hydrogen (C) Alkanes (D) Light hydrocarbons. Answer: A. 27. A cascade control system is a control system in which the output signal of a ( ) regulator is used to control a ( ) control valve. (A) One, two or more (B) Two, one (C) One; the number depends on actual conditions (D) Two, two or more. Answer: A. 28. Regarding the purpose of the handwheel mechanism in pneumatic actuators, which of the following statements is incorrect? (A) As a manual operator (B) To limit the valve opening (C) It allows the elimination of the valve positioner (D) It allows the elimination of the bypass pipeline for the control valve. Answer: C 29. A turbine flowmeter is a type of （ ） flowmeter. (A) Volume (B) Speed (C) Impeller (D) Mass Answer: B 30. The Bourdon tube of a Y—100 pressure gauge is ( ) (A) Oblong (B) Circular (C) Elliptical (D) Semi-circular Answer: A 31. When replacing a 16 MPa pressure gauge, which type of gasket should be used? ( ) (A) Teflon (B) Asbestos (C) Rubber (D) Copper Answer: D 32. 1 Bar is equal to ( ) (A) 1 MPa (B) 1 standard atmosphere (C) 1 engineering atmosphere (D) 105 Pa Answer: D 33. The casing of a shock-resistant pressure gauge has a small hole sealed with rubber; during use, ( ), and its function is ( ). (A) To cut through the rubber for safe pressure release (B) To cut through the rubber to fill it with pressure-resistant oil (C) Not to cut through the rubber, for safe pressure release (D) Not to cut through the rubber, to fill it with pressure-resistant oil Answer: A 34. If the operating range of a pressure gauge exceeds 2/3 of its full scale, then ( ) (A) The joints or welds will leak (B) Its accuracy will decrease over time (C) It will be difficult to read the readings (D) The gauge’s transmission mechanism will deform Answer: B 35. If the operating range of a pressure gauge is less than 1/3 of its full scale, then ( ) (A) The gauge will not display any reading due to low pressure (B) Its accuracy will decrease (C) The relative error will increase (D) The gauge will not be affected Answer: C 36. If the pressure in a container is 2.5 MPa, then the best industrial pressure gauge to use for measuring this pressure should have a range of ( ). (A) 0–2.5 MPa  (B) 0–6 MPa  (C) 0–10 MPa  (D) 0–4 MPa Answer: D
37. To verify an industrial pressure gauge with a range of 0–1.6 MPa and an accuracy class of 1.5, which standard pressure gauge should be used? ( )
(A) 0–1.6 MPa, accuracy class 0.5
(B) 0–2.5 MPa, accuracy class 0.35
(C) 0–1.0 MPa, accuracy class 0.25
(D) 0–1.6 MPa, accuracy class 1.5
Answer: A
38. The test pressure for the strength and tightness of instrument pressure conduits is generally ( ) of the design pressure.
(A) 1.5 times  (B) 1.15 times  (C) 1.25 times  (D) 1.25 times for liquid testing, 1.15 times for gas testing
Answer: D
39. The range of a differential pressure transmitter is 0–100 KPa. If it experiences negative drift of 120 KPa, what will be the instrument’s range and measurement span? ( )
(A) 0–100 KPa, –120–0 KPa
(B) 0–120 KPa, –120–0 KPa
(C) –120–0 KPa, 0–100 KPa
(D) 0–100 KPa, 0–120 KPa
Answer: A
40. When measuring high-pressure forces of 12 MPa, the normal operating pressure should be ( ) of the range.
(A) 1/3  (B) 2/3  (C) 3/5  (D) 3/4
Answer: C
41. When measuring pulsating pressures, the normal operating pressure should not exceed ( ) of the upper measurement limit.
(A) 1/3  (B) 2/3  (C) 3/5  (D) 3/4
Answer: B
42. When measuring steady pressures, the normal operating pressure should not exceed ( ) of the upper measurement limit.
(A) 1/3  (B) 2/3  (C) 3/5  (D) 3/4
Answer: D
43. The maximum length of an instrument pressure conduit should not exceed ( ).
(A) 50 meters  (B) 30 meters  (C) 40 meters  (D) 20 meters
Answer: A
44. When measuring liquid pressures, the pressure tapping point for the conduit should be located at ( ) of the pipe. (A) Topmost part 　　　　(B) Bottommost part 　　　(C) Within an angle of 45 degrees above the center line 　　　(D) Within an angle of 45 degrees below the center line. Answer: D. 45. When measuring the pressure of steam-based media, the pressure tapping point of the pressure conduit should be located at the （　） part of the pipeline. (A) Topmost portion 　　　　(B) Bottommost portion 　　　　(C) Within an angle of 45 degrees above the centerline 　　　　(D) Within an angle of 45 degrees below the centerline. Answer: C 46. When using a standard throttling device for flow measurement, which of the following statements about the fluid is incorrect? ( ) (A) The fluid must fill the circular pipe completely and be continuous. (B) The fluid must be homogeneous and single-phase. (C) Phase change can occur as the fluid passes through the throttling element. (D) The fluid flow rate changes slowly over time. Answer: C 47. The diaphragm chamber of a medium differential pressure transmitter is ( ) compared to that of a high differential pressure transmitter, and ( ) compared to that of a low differential pressure transmitter. (A) larger, smaller 　　　　(B) larger, larger 　　　　(C) smaller, larger 　　　　　(D) smaller, smaller. Answer: A 48. Flow rate is ( ) to the square root of differential pressure, while differential pressure is ( ) to the current output by the transmitter. (A) proportional, inversely proportional 　　　　(B) proportional, proportional 　　　　(C) inversely proportional, proportional 　　　　(D) inversely proportional, inversely proportional. Answer: B 49. If a differential pressure transmitter has experienced negative drift and there is condensation on the positive pressure side, what should be the sequence of operation for the three-valve assembly? ( ) (A) Open the positive pressure valve, close the balance valve, and open the negative pressure valve. 　　　 (B) Open the negative pressure valve, close the balance valve, and open the positive pressure valve. (C) Close the balance valve, open the positive pressure valve, and open the negative pressure valve. 　　 　 (D) Close the balance valve, open the negative pressure valve, and open the positive pressure valve. Answer: A 50. The differential pressure transmitter has experienced negative drift, and there is condensation on the positive pressure side; the correct sequence for shutting down the three-valve assembly should be ( ) (A) close the positive pressure valve, open the balance valve, and close the negative pressure valve. 　　　 (B) Close the negative pressure valve, open the balance valve, and close the positive pressure valve. (C) Open the balance valve, close the positive pressure valve, and close the negative pressure valve. 　　 　 (D) Open the balance valve, close the negative pressure valve, and close the positive pressure valve. Answer: B 51. When installing an orifice plate on a pipeline, if it is installed in the wrong direction, it will cause ( ). (A) An incorrect indication on the differential pressure gauge; (B) No change in the differential pressure gauge’s indication; (C) A reduced indication on the differential pressure gauge; (D) No effect on the differential pressure gauge’s indication. Answer: C 52. The liquid level in an LNG storage tank is measured using a differential pressure transmitter. When there is liquid accumulated on the negative pressure side of the transmitter, the liquid level indication will be ( ). (A) Lower; (B) Higher; (C) Unchanged; (D) Zero. Answer: A 53. In a rotameter, the pressure difference across the rotor is determined by ( ). (A) The flow velocity of the fluid; (B) The pressure of the fluid; (C) The volume of the rotor; (D) The weight of the rotor. Answer: D 54. A rotameter must be installed ( ), with the flow of the fluid going in the direction of ( ). (A) Vertically, from top to bottom; (B) Vertically, from bottom to top; (C) Horizontally, from bottom to top; (D) Horizontally, from top to bottom. Answer: B 55. For a throttle orifice plate flow transmitter, if the current at full scale is 20 mA, then the current at 25% flow rate will be ( ). (A) 8 mA; (B) 12 mA; (C) 5 mA; (D) 9 mA. Answer: B 56. For a turbine flow transmitter, if the output frequency at full scale is 100 Hz, then the frequency at 25% flow rate will be ( ). (A) 80 Hz; (B) 50 Hz; (C) 25 Hz; (D) 75 Hz. Answer: C 57. A turbine flow meter should be installed ( ). (A) Vertically; (B) Either vertically or horizontally; (C) Horizontally; (D) At an angle. Answer: C 58. The ( ) signal output by a turbine flow transmitter is proportional to the flow rate. (A) Frequency (B) Voltage (C) Current (D) Resistance Answer: C 59. The throttling device that meets national standards and can be used directly without calibration is ( ) (A) Standard orifice plate (B) Double orifice plate (C) Venturi tube (D) Elliptical orifice plate Answer: A 60. The minimum flow rate through a throttle orifice plate flow meter should be no less than ( ) of the full scale value (A) 10% (B) 30% (C) 20% (D) 5% Answer: B 61. The normal flow rate through a throttle orifice plate flow meter should be ( ) of the instrument’s full scale value (A) 50–70% (B) 30–50% (C) 80–90% (D) 70–80% Answer: D 62. When using a pressure gauge to measure liquid level, the installation height of the gauge should be ( ) the height of the liquid level zero point. (A) Less than 　　　　(B) Greater than 　　　(C) Equal to 　　　　　(D) Irrelevant. Answer: C. 63. When using the pressure method to measure the liquid level in an open container, the level of the liquid depends on ( ). (A) The location of the pressure measurement point and the cross-sectional area of the container. (B) The location of the pressure measurement point and the density of the fluid. (C) The density of the fluid and the cross-sectional area. (D) The volume of the fluid and the cross-sectional area. Answer: B. 64. When using the differential pressure method to measure the liquid level in a container, the level of the liquid depends on ( ). (A) The location of the pressure measurement point, the cross-sectional area of the container, and the density of the fluid. (B) The pressure difference, the location of the pressure measurement point, and the density of the fluid. (C) The pressure difference, the density of the fluid, and the cross-sectional area. (D) The location of the pressure measurement point, the volume of the fluid, and the cross-sectional area. Answer: B. 65. A float-type level gauge operates based on the principle of ( ). (A) Static pressure (B) Communicating vessels (C) Variable buoyancy (D) Constant buoyancy. Answer: C. 66. The level indication of a float-type level gauge is related to the density of the medium being measured (), while the level indication of a ball-type level gauge is related to the density of the medium being measured (). (A) Related, unrelated (B) Unrelated, related (C) Unrelated, unrelated (D) Related, related Answer: A 67. When using a capacitive level gauge to measure the level of conductive liquids, changes in the liquid level are equivalent to changes in (). (A) Electrode area (B) Dielectric constant (C) Voltage (D) Resistance Answer: B 68. When using a capacitive level gauge to measure the level of a dielectric liquid, changes in the liquid level are equivalent to changes in ( ). (A) Electrode area (B) Voltage (C) Dielectric constant (D) Resistance Value. Answer: A. 69. The temperature of LNG in storage tanks can drop below -100°C, which is equivalent to Fahrenheit ( ). F (A) -173 (B) 173 (C) -148 (D) 212 Answer: C 70. Which of the following statements about bimetallic thermometers is incorrect? (A) A bimetallic strip is composed of two layers of metals with different coefficients of expansion. (B) The scale of a bimetallic thermometer is generally clearer than that of a mercury thermometer. (C) Bimetallic thermometers are resistant to vibration. (D) The layer with the lower expansion coefficient bends toward the layer with the higher expansion coefficient. Answer: D 71. Which of the following statements about flanged transmitters and ordinary differential pressure transmitters is incorrect? ( ) (A) Flanged transmitters respond more slowly than differential pressure transmitters. (B) Flanged transmitters have lower sensitivity than differential pressure transmitters. (C) The measurement range of flanged differential pressure transmitters is limited by the length of the capillary tube. (D) Flanged transmitters are easier to repair than ordinary differential pressure transmitters. Answer: D 72. Which of the following statements about pressure-type thermometers is incorrect? ( ) (A) Pressure-type thermometers consist mainly of a temperature sensing element, a capillary tube, and a Bourdon tube pressure gauge. (B) The greater the coefficient of thermal expansion of the liquid used in the pressure-type thermometer, the more sensitive the instrument. (C) The longer the capillary tube in a pressure-type thermometer, the shorter its response time. (D) The capillary tube in a pressure-type thermometer can be up to 60 meters long. Answer: C 73. Which of the following statements about thermocouples is incorrect? ( ) (A) In a thermocouple temperature measurement circuit, as long as the temperatures at both ends of the connecting wires are the same, the thermoelectric potential of the thermocouple remains constant. (B) The conditions for a thermocouple to generate a thermoelectric potential are that the materials of the two electrodes are different, and the temperatures at the two junctions are different. (C) The thermoelectric properties of a thermocouple are determined by the chemical composition and physical properties of the electrode materials. (D) The magnitude of the thermoelectric potential of a thermocouple depends on the temperatures at both ends and the thickness of the thermocouple wire. Answer: D 74. Which of the following statements about the metal wires used in thermal resistors is incorrect? ( ) (A) Platinum wires are commonly used. (B) Copper wires are also used. (C) Nickel wires are also used. (D) Manganin is sometimes used. Answer: D 75. Which of the following statements about resistance thermometers is inappropriate? ( ) (A) Thermal resistors utilize the principle that the resistance of metals changes in a nearly linear manner with temperature. (B) The resistance wires are made from thicker wires, giving them better shock resistance. (C) Resistance thermometers have the drawback of time delay when measuring temperature. (D) Thermocouples can measure higher temperatures than resistance thermometers. Answer: B 76. Which of the following statements about armored thermal resistors is inappropriate? ( ) (A) They have low thermal inertia and respond quickly. (B) They are flexible. (C) They cannot withstand shocks or impacts. (D) Protected by insulating materials and protective tubes, they have a long lifespan. Answer: C. 77. For two control objects with exactly the same dynamic characteristics, Object A uses PI control while Object B uses P control. When the value of the proportional gain is exactly the same, ( ). (A) System A exhibits more intense oscillations than System B. (B) System B exhibits more intense oscillations than System A. (C) Systems A and B have the same level of oscillation. (D) System A does not oscillate, while System B oscillates intensely. Answer: A. 78. When the proportional gain of a regulator is set appropriately, the variation curve of the controlled parameter is ( ). (A) Divergent oscillation (B) Damped oscillation (C) Oscillation with constant amplitude (D) Aperiodic decay. Answer: B 79. In a pneumatically operated diaphragm control valve that is in operation, if the valve stem becomes disconnected from the valve core, the following phenomenon will not occur: (A) Sudden change in the parameter being regulated (B) The control valve fails to function properly (C) The valve stem does not move (D) The flow rate through the control valve remains unchanged. Answer: C. 80. The transmission distance of a micro-pressure transmitter is generally within ( ). (A) 10m (B) 20m (C) 30m (D) 40m Answer: C 81. When selecting a control valve, the diameter of the valve is determined primarily based on its ( ). (A) Normal flow rate (B) Pipe diameter (C) Flow capacity (D) Fluid viscosity. Answer: C. 82. A gas-operated single-seat valve that is in operation is experiencing high leakage rates; this is usually caused by the following reasons, but one of them is incorrect. Which one is it? (A) Severe wear of the valve core and seat. (B) Air leakage in the actuator diaphragm of the control valve. (C) The valve stem is too long. (D) Excessive pressure difference before and after the control valve. Answer: C. 83. A proportionally controlled electric temperature regulator with a range of 100–200°C, and an output of 4–20 mA; when the indicated temperature changes by 25°C and the regulator’s proportionality factor is 50%, what is the corresponding change in the regulator’s output? (A) 16mA (B) 2mA (C) 4mA (D) 0.8mA Answer: D 84. To reduce zero drift, simple methods include the compensation method and ( ). (A) Positive feedback method (B) Negative feedback method (C) Direct coupling method (D) Indirect coupling method Answer: B 85. To measure the level of liquids that are corrosive or contain crystalline particles, as well as those with high viscosity or tendency to solidify, which method should be used? (A) Pressure-type level gauge (B) Blowing-type level gauge (C) Float-type level gauge (D) Flanged differential pressure transmitter. Answer: D. 86. In actual production, when the installation location of the differential transmitter is above the highest liquid level in the container, what is the relationship between the density of the isolation fluid (ρ2) and the density of the medium (ρ1)? (A) ρ2＞ρ1 (B) ρ2＜ρ1 (C) ρ2=ρ1 (D) ρ2≥ρ1 Answer: B 87. In actual production, when the installation position of the differential gauge is below the lowest liquid level in the container, what is the relationship between the density of the isolation fluid (ρ2) and the density of the medium (ρ1)? (A) ρ2=ρ1 (B) ρ2＞ρ1 (C) ρ2≤ρ1 (D) They are unrelated. Answer: B. 88. When there are large fluctuations in the liquid level inside a container, which device should be used to measure it? (A) External float level gauge (B) Internal float level gauge (C) Float ball level controller (D) Electrocontact level controller Answer: A 89. For torque tube float level gauges of the same model, the greater the measurement range, the larger the diameter of the float. (A) Larger (B) Unchanged (C) Smaller (D) Irrelevant Answer: C 90. The arithmetic mean of random errors will ( ) as the number of measurements increases. (A) Decrease (B) Remain unchanged (C) Increase (D) Irrelevant Answer: A 91. When the bridge is in balance, the product of the resistances in two opposite bridge arms is equal to the （） of the resistances in the other two opposite bridge arms. (A) Product (B) Ratio (C) Difference (D) Sum Answer: A 92. In a thermocouple measurement unit, the automatic compensation for the cold junction temperature of the thermocouple is achieved using ( ). (A) Diode (B) Triode (C) Compound tube (D) Zener diode Answer: A 93. The measurement range of a DDZ-Ⅲ type temperature transmitter is 300–700°C. When the temperature changes from 400°C to 600°C, the transmitter’s output changes from 8 mA to ( ). (A) 10mA (B) 12mA (C) 16mA (D) 20mA Answer: C. 94. When using a DC potentiometer to calibrate a temperature transmitter, the measurement range of the device under calibration is 100–300°C, with a K scale. At an ambient temperature of 20°C, the voltage is 0.798 mV, and at 100°C it is 4.095 mV. Therefore, the zero point should be set to ( ) mV. (A)0 (B)-0.798 (C)3.297 (D)4.095 Answer:C 95. The total resistance of the loop in a thermistor temperature measurement system does not include ( ). (A) The resistance value of the thermal resistor itself (B) Line resistance (C) Resistance of cables and wires (D) Contact resistance of the switch. Answer: D. 96. The resistance value of a platinum resistor Pt100 at 0°C is ( ) Ω. (A)0 (B)20 (C)100 (D)102 Answer: C 97. A thermocouple temperature transmitter receives ( ) signals from a thermocouple. (A)mV (B)mA (C)V (D)A Answer: A 98. The thermoelectromotive force of a thermocouple is a function of the temperature being measured only when the （ ） temperature of that thermocouple remains constant. (A) Hot end (B) Both ends (C) Middle (D) Cold end Answer: D 99. The measurement range of a level differential pressure transmitter is equal to ( ). (A) The sum of the range and the offset (B) The difference between the range and the offset (C) The magnitude of the offset (D) The range. Answer: A. 100. The most basic gate circuit is ( ). (A) NAND gate (B) XOR gate (C) NOR gate (D) AND gate, OR gate, NAND gate. Answer: D. 101. Butterfly valves are particularly suitable for use in ( ) situations. (A) Low differential pressure, large diameter (B) Low differential pressure, large diameter, high flow rate (C) Large diameter, low flow rate (D) High differential pressure, small diameter, low flow rate. Answer: B. 102. After a differential pressure level gauge undergoes negative migration, its range ( ). (A) Increase (B) Decrease (C) Remain unchanged (D) Dependent on the magnitude of the transfer. Answer: C 103. A proportional regulator is essentially an amplifier with a gain factor of ( ). (A) Adjustable (B) Constant (C) Minimum (D) Maximum Answer: A 104. When using a thermocouple to measure temperature in the field, if the polarity of the compensation wire is reversed, the reading displayed by the instrument will ( ). (A) Too large (B) Too small (C) Unchanged (D) Shows a negative value. Answer: A. 105. Differential pressure level gauges undergo zero-point adjustment in practical applications. Whether to use positive transfer or negative transfer depends on ( ). (A) Installation location of the differential pressure gauge (B) Whether condensation will form at the top of the container (C) Density of the medium (D) Ease of maintenance Answer: B 106. It can be used when the load changes are small and no error requirements are specified in the process. (A) Proportional control law (B) Proportional-integral control law (C) Proportional, integral, differential control law (D) Proportional, differential control law Answer: A 107. When the time delay and pure delay of the controlled process are small, the load often experiences large fluctuations, and there is a requirement for no error in the process, then ( ) should be used. (A) P control (B) PD control (C) PID control (D) PI control Answer: D 108. The straight-through single-seat control valve does not have the characteristic of ( ). (A) Low leakage rate (B) Large unbalanced forces acting on the spool in a single-seat valve structure (C) Easy to maintain a sealed condition, and even enable safe shut-off (D) Commonly used in situations with a large pressure difference before and after the valve. Answer: D 109. A straight-through double-seat control valve does not have the characteristic of ( ). (A) It has upper and lower valve cores as well as a bottom valve seat. (B) When the valve is closed, the leakage rate is high. (C) It allows a large pressure difference across the valve cores. (D) When the valve is closed, the leakage rate is low. Answer: D 110. The measuring instrument that does not require mandatory calibration is ( ). (A) Trade settlement (B) Healthcare (C) Residential electricity metering (D) Environmental testing Answer: C 111. The function of an electrical converter is to ( ). (A) Electrical signal converted to electrical signal (B) Gas signal converted to gas signal (C) Electrical signal converted to gas signal (D) Gas signal converted to electrical signal. Answer: C. 112. Miniature control valves have many advantages, but they do not possess the characteristic of ( ). (A) The flow coefficient increases by 30%. (B) The weight of the valve body decreases by 30%. (C) The weight of the valve body increases by 30%. (D) The height of the valve body decreases by 30%. Answer: C. 113. The most basic function of a bipolar junction transistor is to serve as a (). (A) Switch (B) Amplification (C) Unidirectional conduction (D) Voltage regulation. Answer: B. 114. For electric instruments used in petrochemical light hydrocarbon plants, choosing ( ) is the safest option. (A) Flameproof type (B) Isolated type (C) Inherently safe type (D) Explosion-proof type. Answer: C. 115. If the actuator functions in a certain way and the valve core is installed in a particular manner, then such a control valve is considered a wind-shut valve. (A) Positive, positive (B) Positive, negative (C) Negative, positive (D) Positive or negative, positive. Answer: A. 116. An electron potentiometer measures thermal parameters based on the compensation principle of ( ). (A) Voltage (B) Current (C) Resistance (D) Inductance Answer: A 117. A ( ) wiring configuration should be used to connect the thermoresistor to the automatic balance bridge. (A) Two (B) Three (C) Four (D) Five Answer: B 118. In automatic control systems, the result of proportional control often leads to ( ). (A) Error (B) Deviation (C) Dynamic error (D) Static error. Answer: D. 119. The positive terminal of a multimeter’s battery is: (A) The terminal connected to ground; B) The positive terminal (the one where the red test lead is plugged in). 120. Thermocouples are powered by: (A) Direct current; B) Alternating current; C) Three-phase alternating current; D) No power supply. 121. For a measurement transmitter with a range of 6 MP, when the transmitter displays 50%, the measured output value should be ； (D) A) 1MP B) 2MP C) 3MP D) 4MP 122. Among measurement errors, those expressed in terms of error values can be classified as: (A, B) A) Absolute error B) Relative error C) Random error D) Static error 123. Based on the pattern in which errors occur, they can be classified as: (B) A) Absolute error B) Systematic error C) Static error D) Random error 124. Depending on the conditions under which the instrument is used, errors can be classified as: (C) A) Relative error B) Negligible error C) Fundamental error 125. According to the relationship between the measured variable and time, errors can be classified as: (A, B) A) Static error B) Dynamic error C) Relative error D) Negligible error 126. Based on their relationship with the measured variable, errors can be classified as: (B) A) Systematic error B) Fixed-value error C) Additional error D) Negligible error 127. A pressure gauge is considered qualified only when its maximum allowable error (B) corresponds to its accuracy class. A) Greater than B) Less than C) Equal to 128. The accuracy class of a gauge refers to the gauge’s (D) A) error B) basic error C) allowable error D) maximum allowable value of the basic error. 129. The output range of a pressure transmitter is 20~100 KPa; therefore, the maximum value it can measure is (C) A) 99.999 KPa B) 101 KPa C) 100 KPa D) 20 KPa. 130. Under the same differential pressure, the throttling device with the greatest pressure loss is called (B). A) Nozzle B) Orifice plate C) Venturi tube 131. The name of the throttling device used for measuring large-diameter pipes with low fluid pressure inside is (C). A) Nozzle B) Orifice plate C) Venturi tube 132. Capacitive, strain-gauge, diffused silicon, and other types of transmitters are part of the new generation of transmitters, and their advantages are. (A, B, C, D) 1) Simple structure 2) High precision 3) Wide measurement range with low static pressure error 4) Easy to adjust and use 133. The 1151 differential pressure transmitters with different measurement ranges differ due to the measurement diaphragm’s (A). A) Different thicknesses B) Different materials C) Different diameters. 134. When installing a capacitive differential pressure transmitter, attention should be paid to (A, B): A) Severe vibrations B) Corrosion. 135. If the positive and negative pressure conduits of a capacitive differential pressure transmitter are oriented in the opposite direction to those of the positive and negative pressure chambers, it is not necessary to modify the pressure conduits; instead, what angle does the electrical components need to be rotated relative to the measuring diaphragm components? (C) A) 90 degrees B) 360 degrees C) 180 degrees. 136. When measuring the liquid level in an open container using the pressure method, the level of the liquid depends on (B). A) Location of the pressure tapping point and the cross-section of the container B) Location of the pressure tapping point and the density of the medium C) Density of the medium and the cross-section 137. In buoyant level gauges, those that operate based on Archimedes’ principle are (A) A) Floats B) Buoy balls 138. In a float-type steel belt level gauge, if there is a change in liquid level but the pointer does not move, possible causes are (A, B) A) Wear of the gears in the display mechanism B) Looseness between the sprocket and the shaft of the display mechanism C) Loose pointer D) Bent guide tube 139. Possible reasons for errors in the readings of a float-type steel belt level gauge are (B, C) A) Wear of the gears in the display mechanism B) Loose pointer C) Insufficient torque from the constant-force spring or magnetic couple 140. If the float in a torsion tube level gauge breaks, the instrument will indicate (B) A) Maximum value B) Minimum value C) Indeterminate value 141. If the float in a torsion tube level gauge detaches, the instrument will indicate (A) A) Maximum value B) Minimum value C) Unchanged value 142. For level gauges of the same type, the larger the measurement range, the (C) the diameter of the float A) Larger B) Unchanged C) Smaller 143. As the liquid level rises from the lowest to the highest position, the buoyant force acting on the float (A) A) Increases B) Decreases C) Remains unchanged 144. What is the boiling point of water in absolute temperature units? (C) A) -273.16 B) 273.16 C) 373.15 D) 100 145. To increase the upper measurement limit of a mercury thermometer, a gas with a certain pressure is usually filled above the liquid in the capillary tube; this gas is (B) A) Air B) Inert gas C) Oxygen 146. In pressure-type thermometers, the greater the coefficient of thermal expansion of the material used to sense temperature, the (A) the instrument will be A) More sensitive B) Less sensitive C) Unaffected 147. In pressure-type thermometers, the longer the capillary tube, the (B) the response time of the instrument will be A) Faster B) Slower C) Unchanged D) Irregular 148. What is the resistance value of a Pt100 platinum resistor at 0 degrees Celsius? (C) A) 0 ohms B) 0.1 ohms C) 100 ohms D) 108 ohms 149. How to select thermocouples and thermal resistors (A). A) Select according to the temperature measurement range. B) Select according to the ambient temperature. C) Select according to the object being measured. 150. A feedback control system is a closed-loop system (C). A) Not necessarily B) No C) Yes 151. How are constant-value control systems, program control systems, and follow-up control systems classified? (C) A) According to the structure of the automatic control system B) According to the characteristics of the automatic control system C) According to the pattern of change in the set value 152. In a computer control system, the input and output signals of the computer are (B). A) Analog signal B) Digital signal C) 4–20mA standard signal 153. In a computer-controlled system, after receiving field signals and performing calculations, judgments, and processing, the host makes various control decisions; in what form are these decisions outputted? (C) A) Decimal B) Hexadecimal C) Binary 154. In a DCS system, DO stands for: (C) A) Analog input B) Analog output C) Digital output 155. The compensation wire should be installed starting from the thermocouple and extending up to (C). A) On-site junction box B) Secondary instruments C) A location at the same temperature as the cold-end compensation device. 156. When using an orifice plate to measure flow rate, the orifice plate should be installed (A) in front of the control valve, B) behind it, or C) at any position. 157. The determination of the forward and reverse action of a controller in a control system is based on (B) A) the safety of production, B) achieving negative feedback in the closed-loop system, or C) having an appropriate system gain. 158. 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 (A). A) Rising B) Falling C) Unchanged 159. The main purpose of adding differential action to a regulator is (C). A) Overcoming the pure lag of the object B) Overcoming the inertial lag of the object C) Overcoming both the inertial lag and the easy lag of the object. 160. For differential pressure flow meters, if the negative pressure pipeline is blocked, the gauge will indicate (A). A) Too large B) Too small C) Unchanged Fill-in-the-blank question: 1. In a thermocouple temperature measurement circuit, as long as the temperatures at both ends of the display instrument and the connection wires are the same, the (total potential value) of the thermocouple will not change due to their inclusion, and this is a conclusion drawn from the (intermediate conductor) law. 2. The conditions for a thermocouple to generate a thermoelectromotive force are (different materials for the two thermal electrodes) and (different temperatures at the two junctions). 3. Among the three types of thermocouples with classification codes S, K, and E, their potentials at 100°C are (0.645 mv), (4.095 mv), and (6.317 mv) respectively. 4. When using a thermocouple to measure temperature, its connection wires should be (compensation wires). 5. The compensation wire is an extension of the thermocouple, but the cold end of the thermocouple must be considered for (compensation). 6. A elastic pressure gauge operates on the principle that the (deformation) of an elastic element is proportional to the (pressure applied) to it. 7. Commonly used elastic pressure gauges include (diaphragm) type, (bellows) type, and (spring tube) type. 8. Diaphragm pressure gauges are mainly composed of a (measurement system), a (transmission system), an (indication system), and a (case connector) section. 9. Precision pressure gauges have a high level of accuracy, typically ranging from (0.6), (0.4) to (0.25) grade. 10. The electric contact pressure gauge can emit an alarm signal when the pressure is below the lower limit or above the upper limit. 11. Piston pressure gauges are generally divided into single-piston and double-piston types, and their working principle is (static pressure balance). 12. The weights on a piston pressure gauge indicate (pressure). 13. Gas pressure transmitters can be divided into two main categories: those based on the (displacement balance) principle and those based on the (force balance) principle. 14. 1 kilogram-force = (9.8) Newtons. 1 MPa = (10×6) Pa. 15. The volume of fluid that passes through in a unit of time is called (volumetric flow rate), and it is denoted by (Q). 16. The density of a gas decreases as (temperature) increases, and increases as (pressure) increases. 17. Pneumatic differential pressure transmitters generally operate on the principle of (torque balance). 18. A pneumatic differential pressure transmitter is structurally composed of a (measurement) unit and a (force-to-air conversion) unit. 19. The diaphragm chamber of the differential pressure transmitter is filled with (silicone oil), which, in addition to transmitting pressure, also provides (damping) effect, thereby ensuring a stable output from the instrument. 20. The glass level gauge operates based on the (communicating vessels) principle. 21. A static pressure level gauge operates based on the principle of fluid (static pressure) equilibrium. 22. In the model number of a flanged differential pressure transmitter, an “A” indicates that (positive) offset adjustment is possible, while a “B” indicates that (negative) offset adjustment is possible. 23. The level measurement of a float-type level gauge is based on the (Archimedes) principle. 24. The float-type level gauge operates on the principle of (constant buoyancy). 25. When a 220VAC voltage is applied to a 10-ohm resistor, the current flowing through this resistor should theoretically be (22A). 26. Depending on the impurities added to semiconductors, doped semiconductors can be divided into two categories: (N)-type semiconductors and (P)-type semiconductors. 27. The characteristics of a PN junction are (unidirectional conductivity) and (capacitance effect). 28. There are two types of diode breakdown: one is (avalanche) breakdown, and the other is (Zener) breakdown. 29. The three most basic logical operations in digital circuits are (AND), (OR), and (NOT). 30. An automatic control system mainly consists of four major components: (controller), (control valve), (controlled object), and (transmitter). 31. Automatic control systems can be classified according to the control laws inherent in the controllers; common types include (proportional), (proportional-integral), (proportional-differential), and (proportional-integral-differential) control systems. 32. During the measurement process, the difference between the value read by the instrument and the true value is known as (measurement error). 33. A system in which there is a feedback loop between the quantity to be regulated output by the system and the input side is a (closed-loop) system. 34. The ratio of the maximum flow rate Qmax that a control valve can regulate to its minimum flow rate Qmin is called the (adjustability ratio) of the control valve, denoted by R. 35. In physics, the liquid level of a fluid is denoted by (L). 36. The flow rate of a fluid is in a (square root) relationship with its pressure. 37. When the pressure difference before and after the control valve is small and low leakage is required, a (single-seat) valve is generally suitable. 38. For regulating low differential pressures and high-flow gases, a (butterfly valve) can be used. 39. When both regulation and cutoff are required, an (eccentric rotary) valve can be used. 40. The feed water control valve for the steam drum should be of the (air-operated shut) type or equipped with an additional hold-down valve. 41. A (valve positioner) is required in situations where the friction of the control valve is high and precise positioning is needed. 42. Valve positioners in pneumatic control valves include (electrical) valve positioners and (pneumatic) valve positioners. 43. Programmable regulators use international standard analog signals, namely voltage (1–5V) and current (4–20mA). 44. The PMK programmable regulator consists of three types of modules, namely the (input module), the (control calculation module), and the (output module). 45. In the field of automation, a condition in which the parameters being regulated do not change over time (a steady state) is referred to as the static state of the system. 46. In a dynamic system, stability is (temporary), (relative), and (conditional). 47. In a thermistor thermometer, R0 and R100 represent the resistance values at (0°C) and (100°C), respectively. 48. The five key parameters in instrument measurement are (temperature), (pressure), (level), (flow rate), and (online analysis). 49. The level of the boiler drum is generally controlled using a three-element level control system that takes into account (feedwater flow rate), (steam flow rate), and (drum level). 50. 250 Pa = (25) mmH2O 51. Feedback is divided into (positive) feedback and (negative) feedback. 52. In a pipe, the fluid velocity is generally highest at the (centerline of the pipe), and it is zero at the (pipe wall). 53. If the (Reynolds number) is the same, the flow of the fluid is similar. 54. The diaphragm box of medium differential pressure transmitters is larger than that of high differential pressure transmitters, but smaller than that of low differential pressure transmitters. 55. Rotameters belong to (constant pressure) drop flow meters. 56. A turbine flowmeter is a (velocity) type of flowmeter. 57. Turbine flow transmitters should be installed (horizontally). 58. When using a pressure gauge to measure liquid level, the installation height of the gauge should be the same as the height of the zero liquid level; otherwise, the (height difference) must be corrected. 59. 100°C on the Celsius scale is equivalent to 212°F on the Fahrenheit scale. 60. The higher the temperature, the greater the resistance value of materials such as platinum, nickel, and copper. 61. The I/A’s of the distributed control system are products of (FOXBORO) company. 62. The lower the operating power of a relay, the higher its sensitivity. 63. The ideal adjustability ratio of a control valve depends on (the valve core structure). 64. The actual adjustable ratio depends on the (valve core structure) and (piping conditions) of the control valve. 65. Process control computer software is divided into (system software) and (application software). 66. Based on the function of integrated circuits, they are divided into (digital integrated circuits) and (analog integrated circuits). 67. The process of converting alternating current into direct current is (rectification). 68. Typical rectifications include (single-phase half-wave rectification) and (bridge rectification). 69. Another source of digital signals is the use of various digital instruments to measure physical quantities such as (temperature), (pressure), (flow rate), (speed), etc., which generate digital or pulse signals. 70. Digital signals do not require (A/D) conversion and can be connected to a (computer) directly via digital input interfaces. 71. To enable a microcomputer to control the production object, the calculation results must be sent to the corresponding (actuator). 72. The signals required by actuators are divided into (continuous control voltage and control current signals) and (digital or switch signals). 73. The continuous control voltage and control current signals required by the actuator are applied to various (control valves), (display recorders), (servo mechanisms), etc. 74. A (air-shut) control valve should be used at the compressor inlet, while a (air-open) control valve should be used in the heating furnace fuel gas system. 75. The three main components of a relay are the (receiving mechanism), the (intermediate mechanism), and the (actuating mechanism). 76. The greater the proportionality of the regulator, the smaller the amplification factor; the control effect becomes weaker, and the residual error increases. 77. The main items for calibrating pneumatic control valves include four aspects: (basic error), (hysteresis), (setpoint deviation), and (nominal stroke deviation). 78. The common methods for pipe connection are (threaded connection), (flange connection), and (welding). 79. The I/Asevies system control loop of FOXBORO Company consists of (Block) and (Compound) in the control processor. 80. Given that the instrument reading is 495°C and the correction value is +5°C, the absolute error in the measured temperature is (-5°C), while the actual temperature of the medium being measured is (500°C). 81.1 mmH2O is the pressure generated by 1 millimeter of water column in pure water at a temperature of (4)°C. 82. To avoid disturbance to the liquid caused by the valve, the flow control valve should be installed behind the instrument under test. 83. In interlock systems, if it is required that the on-site self-protection solenoid valve remain energized under normal conditions and lose power during self-protection, the (normally closed) contacts of a relay should be used. 84. In automatic control systems, the first character of an instrument tag indicates F for (flow rate) and D for (density). 85. The basic logical operations in digital circuits are (AND), (OR), and (NOT). 86. If the positive-pressure pipeline of a differential pressure flow meter is blocked, the instrument reading will be low; if the positive-pressure nozzle of a differential pressure gauge with backflow ventilation is blocked, the instrument reading will be high. 87. The instrument device installed on a pipeline that detects a set pressure and sends an alarm signal is a (pressure switch). 88. The fuel gas system of the heating furnace should use (air-open) type control valves, while its feed system should use (air-close) type control valves. 89. A differential pressure flow meter consists of three parts: (throttle device), (pressure guide tube), and (transmitter). 90. Common cables are divided into (power cables) and (control cables). 91. An interlocking circuit usually consists of an (input) section, a (logic) section, and an (output) section. 92. Depending on the unit of the error itself, errors can be classified into (absolute) error, (relative) error, and (reference) error. 93. When measuring liquid pressure, the pressure tapping point should be located in the (lower) half of the pipeline; a (gas collector) should be installed at the highest point of the pressure conduit. When measuring gas pressure, the pressure tapping point should be placed in the (upper) half of the pipeline, with a (gas-liquid separator) installed at the lowest point of the pressure conduit. 94. For flow measurement devices, the length of the straight pipe section ahead of the instrument under test can range from (30) to (50) times the diameter of the flow meter’s flow tube, while the length of the straight pipe section behind the instrument under test should be between (10) and (15) times the diameter. 95. The (frequency) of the output signal from the turbine flow transmitter is proportional to the flow rate. 96. Linear electric actuators are typically used to operate (direct-acting single-seat valves), (double-seat valves), (three-way valves), (corner valves), etc.; they are installed directly on the (valve body) and connected to the (valve stem). 97. The most widely used industrial nuclear instruments are (level gauges), (density meters), (thickness gauges), and (nuclear scales). 98. The common parameter tuning methods for automatic control systems include (empirical method), (attenuation curve method), (critical proportionality method), and (response curve method). 99. To measure the current in a circuit, the ammeter must be connected in series with that circuit. To ensure that the connection of the ammeter does not affect the original state of the circuit, the (internal impedance) of the ammeter itself should be as low as possible. 100. The methods for constructing an A/D converter include: (counting A/D conversion), (successive approximation A/D conversion), (double integration A/D conversion), (parallel A/D conversion), and (serial-parallel A/D conversion). Question and Answer: 1. What is a power source? Answer: In a circuit, the component that can provide energy. 2. What is a load? Answer: In a circuit, the component that consumes energy is called a load. 3. What is direct current? Answer: The magnitude and direction of the current do not change over time; the amount of charge that passes through the cross-section of the conductor per unit of time remains constant, and its direction also never changes. 4. Explain Ohm’s law: Answer: The current I flowing through a resistor R is directly proportional to the voltage U across the resistor, and inversely proportional to the resistance R itself. This principle is known as Ohm’s law, expressed as I = U/R. 5. What is a short circuit? Answer: The power supply is directly connected to each other through the two wires of the load, without passing through the load itself. 6. What is a circuit breaker? Answer: In a circuit, current cannot flow because the wires are not connected to each other, which results in no voltage drop across the load and other components. 7. Explain automatic control systems: Answer: They refer to systems in which the output remains at a constant value or changes over time in response to various requirements. 8. What is the object being called? Answer: It refers to the production process corresponding to the physical quantity being regulated, or the equipment and devices used to carry out that production process. 9. What is a given value? Answer: According to production requirements, the value that the regulated quantity must reach is specified. 10. What is a closed-loop system? Answer: A system in which there is a feedback loop between the quantity to be regulated supplied by the system and the input terminal. 11. What is an open-loop system? Answer: The measured quantity is not fed back to the input side of the system in any form. 12. Superposition principle of linear systems: Answer: If several inputs act on a system simultaneously, the overall effect at the output is equal to the sum of the effects produced by each input acting alone. 13. What is a host? Answer: It is the core component of a computer’s entire system; all other devices operate under its control. 14. What is software? Answer: The entire process of deciding what a computer should do and how to do it, and making these decisions understandable to the computer. 15. How do conductors conduct electricity? Answer: The electrons in a conductor move in a directed manner under the influence of an external electric field, thereby forming an electric current. 16. Why does a PN junction have a capacitive effect? Answer: Because there is a certain charge on each side of the PN junction, and this charge changes when the applied voltage changes. 17. How to use a multimeter to measure the resistance of a resistor? Answer: 1) Select the resistance setting on the multimeter based on the approximate resistance value of the resistor ； 2) Adjust the zero point of the multimeter ； 3) Connect the two probes of the multimeter to the two sides of the resistor to take a measurement. 4) If the resistance range selected on the multimeter is too high or too low, select it again and repeat the above steps. 18. What are the typical values of the dead zone voltage for silicon diodes and germanium diodes? Answer: The dead zone voltage of silicon diodes is approximately 0.5V. The dead zone voltage of a germanium diode is approximately 0.2V. 19. What are the several configuration types of transistor amplifier circuits? Answer: There are three configuration types of transistor amplifier circuits, namely common-emitter amplifier circuits, common-collector amplifier circuits, and common-base amplifier circuits. 20. What is the purpose of introducing negative feedback in an amplification circuit? Answer: Negative feedback is introduced in amplifier circuits to improve the performance of the amplifier, including its static and dynamic performance. 21. What are the types of negative feedback amplifier circuits? What is its function? Answer: Negative feedback amplifiers consist of voltage and current feedback, and there are four types of feedback combinations: series and parallel. Voltage negative feedback can stabilize the output voltage ； Current negative feedback can stabilize the output current ； Series negative feedback can increase the input resistance ； Parallel negative feedback can reduce the input resistance. 22. What are the main aspects of chemical process automation? Answer: Chemical process automation generally includes an automated monitoring system ； Automated signaling and interlock protection systems ； Automatic control and automatic start-stop systems ； Automatic adjustment system. 23. Instruments for measuring pressure can be classified into several categories based on their conversion principles; what are they? Answer: Instruments for measuring pressure can be divided into four major categories based on their conversion principles, namely: 1) Manometer type pressure gauges ； 2) Spring pressure gauge ； 3) Electrical pressure gauge ； 4) Piston pressure gauge. 24. What are the main types of level measurement instruments based on their working principles? Answer: 1) Direct-reading level gauge ； 2) Differential pressure level gauge ； 3) Float-type level gauge ； 4) Electromagnetic level gauge ； 5) and radial level gauges ； 6) Acoustic level gauge ； 7) Optical level gauge. 25. What is temperature? Can temperature be measured directly? Answer: Temperature is a measure of how hot or cold an object is. Temperature cannot be measured directly; it can only be determined indirectly by means of heat exchange between objects at different temperatures, as well as by the property that certain physical characteristics of objects change depending on their temperature. 28. What is a pressure thermometer, and on what principle does it work? Answer: A instrument that measures applied pressure as a function of temperature is called a pressure thermometer. It is based on the liquid in a closed system. It is based on the principle that the saturated vapor of a gas or a liquid with a low boiling point expands in volume or experiences a change in pressure when heated; a pressure gauge is used to measure this change, thereby determining the temperature. 29. Why is the sensing element of a differential pressure transmitter designed as a diaphragm box structure? Is a single diaphragm sufficient? Answer: Because the diaphragm box assembly exhibits excellent sensitivity and linearity within the operating differential pressure range; when the differential pressure exceeds this range, that is, in the case of one-way overload, the diaphragm box not only remains intact but also suffers very little impact ； Since the diaphragm box is filled with silicone oil, in addition to transmitting pressure it also provides damping, resulting in a stable output from the instrument ； It can be seen from the above that a single diaphragm cannot withstand one-way overload; although it is easy to manufacture and has high sensitivity, it is not suitable for use. 30. What are the methods for calibrating float level gauges? Answer: There are mainly two methods: the tank liquid method and the weight hanging method. On-site, the liquid calibration method is generally used; if the liquid to be measured is not water or alcohol, it can be calibrated using density conversions for other liquids. During maintenance, the weight-hanging calibration method can be employed. During verification, remove the float, attach a weight plate, calculate the values at the starting, middle, and ending points of the float, and perform addition code verification. 31. What are the three elements of a temperature scale? Answer: 1) The equilibrium temperatures of some pure substances were selected as the reference points for the temperature scale ； 2) Specifies the reference instruments for different temperature ranges ； 3) An interpolation formula for the relationship between the indication of the reference instrument and the International Temperature Scale was established. 32. Among the three types of thermocouples with classification codes S, K, and E, which one has the highest potential at 100 degrees Celsius? Which one is the smallest? Answer: At 100 degrees, the electromotive force of grade S is 0.645 mv ； At 100 degrees, the electromotive force for division number K is 4.095 mv ； At 100 degrees, the electromotive force of division E is 6.317 mv. Therefore, E has the highest thermoelectric potential, K is next, and S has the lowest. 33. Are the thermoelectric properties of the compensation wire exactly the same as those of the thermocouple it is matched with? Answer: Compensation wires are cheaper than thermocouples. Within the range of 0–100 degrees, their thermoelectric properties are identical to those of the associated thermocouple. Therefore, using a compensation wire is like extending the thermocouple’s cold end to a control room or another location where it is convenient to take readings, and which is far away from the heat source ； However, strictly speaking, the compensation wire and the thermocouple potential are not exactly the same. For example: the compensation wire made of copper-constantan has a potential of 4.27 mV at 100 degrees, while the corresponding K-type thermocouple has a potential of 4.095 mV ； The compensation wire is copper-nickel-copper; its potential at 100 degrees is 0.643 mV, whereas that of the matching S-type thermocouple is 0.645. 34. What are the categories of complex regulatory systems? Answer: There are many types of complex control systems. Based on the structure of the system and the tasks it performs, common complex control systems include cascade, proportional, ratio, split-range, feedforward, substitute, and three-variable control systems. 35. Can the signal circuit ground, the shielding ground, and the protection ground be shared? Answer: The ground for the signal circuit (operating ground) and the shielding ground can share the same grounding grid, but they should not be connected to the protection grounding grid; a separate grounding grid should be established, with a grounding resistance of no more than 10 ohms. 36. What is absolute error? Answer: It is the difference between the measurement result and the true value. 37. What is relative error? Answer: It is the ratio of the absolute error to the measured value. 38. What is citation error? Answer: It is the ratio of the absolute error to the range value. 39. When adjusting a differential pressure transmitter, do the zero point and range affect each other? Answer: When adjusting the range, the force balance is altered, which affects the zero point. When adjusting the zero point, although it also causes changes in the position of elastic elements such as diaphragms, sealing membranes, and tension rods, thereby generating additional forces, these forces are very small and generally do not affect the measurement range. 40. Why is silicone oil generally used as the filling fluid for the capillaries of flange level gauges and the diaphragm boxes of differential pressure transmitters? Answer: Because silicone oil has a high boiling point, a low coefficient of expansion, a low freezing point, and low chemical reactivity, changes in ambient temperature do not affect the measurement accuracy. 41. What is an input? Answer: It generally refers to various signals fed into an automatic control system, including setpoints and disturbances. 42. What is feedback? Answer: Returning all or part of the output signal to the input is called feedback. 43. What is interference? Answer: Various external factors that cause changes in the quantity being measured within an object are called disturbances. 44. Among the two throttling devices, orifice plates and Venturi tubes, which one has a greater pressure loss when the differential pressure is the same? When the pipe diameter and differential pressure are the same, which one has a larger flow rate? Answer: For the same differential pressure, the pressure loss of an orifice plate is 3 to 5 times greater than that of a Venturi tube. When the pipe diameter and differential pressure are the same, the Venturi tube has a higher flow coefficient, and thus a higher flow rate. 45. What are the characteristics of a feedforward control system? Answer: 1) Feedforward regulation is carried out based on the magnitude of the disturbance. If benefits are to be obtained from a node, it is generally necessary to act more promptly than through feedback regulation. 2) Feedforward control is an “open-loop” control system. 3) Feedforward control uses \"specialized\" controllers determined by the characteristics of the object. 4) A feedback mechanism can only overcome one type of interference. 46. How does a bimetallic thermometer work? What are its features? Answer: It consists of two pieces of metal with different coefficients of expansion that are firmly bonded together; one end is fixed, while the other end is connected to the pointer through a transmission mechanism. When the temperature changes, due to different expansion coefficients, the bimetallic strip undergoes angular displacement, which causes the pointer to indicate the corresponding temperature. This is the working principle of a bimetallic thermometer. Bimetallic thermometers have a simple structure, are inexpensive, easy to use, resistant to vibration, free from the \"mercury hazards\" associated with mercury thermometers, and have scales that are clearer than those of mercury thermometers; therefore, they are widely used. 47. During a shutdown for maintenance of a certain heating furnace, it was found that the thermocouple sheath used to measure the furnace temperature could not be removed. What is the reason for this? Answer: This is because the thermocouple protection sleeve bent at the measured temperature. Therefore, when installing temperature sensors in high-temperature equipment such as heating furnaces, it is best to install them vertically; if horizontal installation is necessary, then when the insertion depth is greater than 1 meter or the temperature to be measured is above 700 degrees, a support should be used to hold the sensor in place. 48. What is protective grounding? Answer: Grounding that is provided to prevent dangerous voltages, which may arise from accidents such as insulation failure on electrical meters and the metal parts of electrical equipment, from posing a threat to human safety, is called protective grounding. 49. Which devices should be protected by grounding? Answer: Those that require protective grounding include the instrument panel and its base, the enclosures of electrical instruments, distribution boxes, junction boxes, cable trays, conduit pipes, and the shielding layer of armored cables. 50. What is working ground? Answer: The grounding provided to ensure the accuracy of instruments and their safe and reliable operation is called the working grounding of the instrument system. 51. What does working ground include? Answer: Working ground includes signal circuit grounding, shielding grounding, and intrinsically safe instrument grounding. Its purposes are to provide a potential reference point, suppress interference, and ensure explosion protection. 52. Does DCS require no maintenance to operate properly during production? Answer: No. It is also necessary to regularly delete some of the unnecessary files, so as to prevent them from taking up hard drive space and affecting the machine’s performance. Additionally, the historical records of some important operational parameters should be archived and copied to a tape drive as documentation. 53. What are the steps to deactivate a differential pressure transmitter? Answer: 1. Slowly close the positive pressure valve. 2. Simultaneously open the balance valve. 3. Then slowly close the negative pressure valve. 4. Close the primary pressure tapping valve. 54. What are the common methods used for cold junction compensation of thermocouples? Answer: 1. Freezing point method 2. Calculation method 3. Equilibrium bridge method 4. Mechanical zero adjustment method 55. In what applications are two-position four-way solenoid valves used? Answer: Two-way four-position solenoid valves are used in double-acting cylinder actuators and piston actuators to automatically switch and control the opening and closing of control valves, and they are widely employed in sequential control systems. 56. What are the characteristics of pneumatic long-stroke actuators? Answer: Pneumatic long-stroke actuators are characterized by a long stroke and high torque; they convert air signals of 20–100 Kpa into corresponding angles (0–90º) or displacements (200–400 mm). They are suitable for use in angle-control valves, as well as in butterfly valves, gate valves (air dampers), etc., which require high torque. 57. Into which categories can control valves be classified based on their structural form? Answer: 1. Straight-through single-seat control valve 2. Straight-through double-seat control valve 3. Angle valve 4. Triangular valve 5. Diaphragm valve 6. Low-temperature control valve 7. Butterfly valve. 58. The output of a float level gauge sometimes fails to reach 100 Kpa; analyze the reasons for this. Answer: 1. Insufficient air supply; 2. Leak in the blower of the transmitter; 3. Leak in the packing of the transmitter; 4. Misalignment of the linkage; 5. Leak in the output pipeline. 59. How to verify the rated travel deviation of a pneumatic control valve? Answer: By introducing a 120% signal into the actuator’s air chamber, the ratio of the additional travel of the valve stem from 100% to 120% signal to the rated travel is known as the rated travel deviation (this is intended to ensure that the air-operated valve closes fully). 60. How to check for grease in the oxygen pressure gauge? Answer: When calibrating the oxygen pressure indication, first check whether there is any grease inside the gauge. The method is to first pour pure warm water into the spring tube, shake it, and then pour the water into a container filled with clean water; if there are no colored oil stains on the surface of the water, it can be assumed that there is no grease present. Calculation problem 1) The internal resistance of an electrical appliance is 24 ohms. The voltage applied across it is 60 V, 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 converter, 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 converter, since ΔQ = K × ΔP, the differential pressure for 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 testing the 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. 6) 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. 7) 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 thermoelectric potential 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 at 977°C is also obtained. 8) 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 for flow rates of 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. 9) 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 counts 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. 10) 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. 11) 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. 12) 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. 13) 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. 14) Calculate the total resistance inside a junction box with 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. 15) 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. 16) 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. 17) 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 1118°C. 18) 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. In this case, I = 4 + (20-4)/162 × 122 = 13 mA. Answer: The output signal is 13 mA. 19) 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 lights can be connected in series. The current is I=U/R=24/(5×2)=2.4A. The current flowing through each indicator light is 2.4A. 20) 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. 21) 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 scale points were all less than 1.4 KPa. Is this pressure gauge qualified? Solution: The maximum reference error of this table = ×100% = 1.4%