Thread Content
Instrument Technician Test Questions I. Fill in the blanks: 1. When measuring steam flow, deformation of the baffle can cause the indication to ________, while the presence of gas on the positive pressure side can cause the indication to ________. Answer: Low, Low. 2. If the zirconia probe signal is high, then the measurement result will be __________. Answer: Low. 3. The definition of the flow coefficient C is: when the control valve is fully open, the pressure difference before and after the valve is __________, the density of the fluid is ___________, and every __________, the amount of fluid that passes through is ___________. Answer: 100KPa, 1gf/cm3, hours, cubic meters. 4. The instrument tag LICA refers to ____________________. Answer: Level indication, regulation, and alarm. 5. The characteristic of intrinsically safe instruments is that, whether in normal operation or in case of failure, the sparks generated by the circuits and systems, as well as the temperatures reached, will not cause __________ to explode. Answer: Explosive mixture. 6. When a test pen is used to distinguish between direct current and alternating current, the situation where both poles of the neon tube emit light is __________, while the situation where only one pole of the neon tube emits light is __________. Answer: Alternating current, Direct current. 7. The attenuation ratio of an ideal regulation process is __________. Answer: 4:1. 8. To measure the current in a circuit, the ammeter must be _________ to that circuit. In order 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 _________ as possible. Answer: Series, small, 9. Control valves can be classified into ____________, ____________, and ____________ based on their source of energy. Answer: Pneumatic control valve, Electric control valve, Hydraulic control valve. 10. The maximum deviation refers to the greatest extent to which the controlled parameter deviates from ___________ during the transition process. Answer: The given value is 11. When measuring the pressure of corrosive media, _________ must be added to prevent corrosion. Answer: Isolation tank 12. A direct-acting pneumatic regulator with the control point set at 60 kPa. If the integral valve is closed, and the proportionality setting is set at 50%, then when the measured value is 50 kPa while the setpoint is 60 kPa, the output value will be 35 kPa. The proportionality error in this case is __________. Answer: 10% 13. When an electrometric potentiometer is used as a temperature measuring instrument, once the thermocouple’s thermoelectric temperature stabilizes, the length of the compensation wire affects the measurement of ________. Answer: None. 14. A constant-value control system is regulated according to ________________, and it is a __________ loop control. Answer: The magnitude of the deviation from the given value is measured. Closed loop. 15. Feedforward control is carried out according to ______________, and it is a __________ loop control. Answer: The magnitude of the perturbation; 16.__________ Control systems generally do not use valve positioners. Answer: Traffic 17. When using a drill to machine workpieces that require high precision, the rotation speed should be __________ compared to when machining workpieces that require lower precision. Answer: High. 18. The control valve at the compressor inlet should be of the __________ type. Answer: Air shut-off 19. For the storage tank level control system, when the control valve is installed on the outlet pipeline, the _________ type should be selected ； When installed in the inlet pipeline, the _________ type should be selected. Answer: Gas on, Gas off. 20. The differential gain of the positive differential regulator is 6, and the differential time scale is 60 seconds. Assuming that the output is 0% at the initial stage, then when the signal changes by 10%, the output should jump to __________% . Answer: 60 21. The three-pulse level control system for boiler drum incorporates a ____________ signal on top of the two-pulse control mechanism. Answer: Water supply flow rate 22. The dual-pulse level control system for the boiler drum introduces ____________ as a feedforward signal based on single-pulse control. Answer: Steam flow rate 23. In the three-element level control system for the boiler drum, ____________ is the controlled variable and serves as the primary signal. Answer: Drum water level 24. Insulating tape (black tape) is used for insulating and wrapping the joints of wires and cables with alternating current voltages below ________V. Answer: 380 25. Increasing the proportional gain P of the regulator from 100% to 200% will make the system more _________ stable. Answer: Increases by 26. The higher the temperature, the more ________ the resistance value of materials such as platinum, nickel, and copper. Answer: Large 27. The commonly used temperature sensing elements are __________ and __________. Answer: Thermocouple, Thermal resistor. 28. A simple control system consists of four main components: __________, ___________, __________, and __________. Answer: Controlled object, transmitter, regulator, and control valve. 29. Electric Type III instruments are powered by __________, the signal transmitted at the field level is __________, while the signal transmitted to the control room is __________. Answer: 24VDC, 4-20mADC, 1-5VDC. 30. Valve positioners are generally used in situations where the pressure difference before and after the valve is greater than __________, in fluids that contain __________ or are highly viscous, and on control valves with a diameter of __________ or more. Answer: 10Kgf/cm2, suspended particles, 100mm. 31. When putting a cascade control system into operation, the _________ loop should be activated first, followed by the _________ loop. Answer: in series; main; 32. To measure the current in a circuit, the ammeter must be _________ to this circuit. In order 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 _________ as possible. Answer: Series, small. 33. After the thermocouple wire breaks, the temperature indication __________. Answer: Maximum 34. The transmission signal in the input circuit from the field to the control room is a __________ signal. Answer: 4–20 mADC. 35. The higher the precision of an instrument, the more ________ its sensitivity, and the more ________ its sensitivity limit. Answer: High Low 36. Measurement instruments usually use __________ and __________ to determine the magnitude of dynamic error. Answer: Time constant, Damping time. 37. The characteristics of an object can be represented by three parameter values: __________, __________, __________. Answer: Amplification factor K, time constant T, delay time τ. 38. The static characteristics of commonly used control valves include __________, __________, __________, and __________. Answer: Linear, Equal percentage, Parabolic, Fast opening. 39. When the change in the indication of a proportional regulator is the same, the smaller the proportionality gain, the more _____ the output change; if the proportionality gain remains unchanged, the larger the indication value, the more _____ the output. Answer: Large, Large, 40. If the zirconia probe signal is high, then the measurement result will be __________. Answer: Low. In a cascade control system, the secondary controller is usually a __________ controller, while the primary controller is a __________ controller. Answer: Ratio, Proportional integration. 42. If the two materials making up the thermocouple circuit are the same, then regardless of the temperature of the thermocouple, the total electromotive force within the thermocouple circuit is __________. Answer: Zero. 43. When a wire made of a third material is inserted into the thermocouple circuit, as long as the temperatures at both ends of this third wire are the same, the inclusion of this third wire has ______ effect on the thermoelectric potential of the thermocouple. Answer: No. 44. When measuring gas pressure, the pressure tap should be located at the _________ of the pipeline. Answer: Upper half. 45. When the pressure under measurement is stable, its normal value should be at ______ within the measurement range of the pressure gauge; when the pressure under measurement fluctuates frequently, its normal value should be at ______ within the measurement range of the pressure gauge. Answer: 2/3, 1/2. 46. The electromotive force of thermocouple AB is _________ to the intermediate temperature of materials A and B, and is only _________ to the endpoint temperatures t and t0. Answer: Irrelevant; Relevant. 47. Pneumatic control valves are divided into two types: air-open and air-close. The type in which the valve closes when there is signal pressure and opens when there is no signal pressure is the ________ type, while the type in which the valve opens when there is signal pressure and closes when there is no signal pressure is the ________ type. Answer: Gas off, Gas on. 48. The regulation patterns of the regulator include __________, __________, __________, __________, __________. Answer: Two-position control, proportional control, proportional-integral control, proportional-differential control, proportional-integral-differential control. 49. The electric type III regulator is used to receive the ______ measurement signals from transmitters or converters as input signals; these signals are compared with the ______ setpoint signals to generate a deviation signal. This deviation signal is then subjected to ______, ______, and ______ operations, and the resulting ______ is sent as the output signal, thereby enabling automatic control of the process parameters. Answer: 1—5VDC. 1—5VDC: proportional, integral, differential. 4—20mADC. 50. The differential pressure acting on a differential pressure flow meter is proportional to ____________. Answer: The square of the fluid flow rate. 51. ________ feedback is used in all automatic control systems. Answer: -52. The automated components in an automatic control system include ________. ________ and ________ as three parts. Answer: Transmitter, regulator, control valve. 53.1 MPa = ________ Pa = ________ Kgf/cm2 = ________ mmH2O. Answer: 106, 10, 105, 54. When used in pressure guiding tubes for flow measurement, if there is a leak in the valve or pipeline on the positive pressure side, the instrument will indicate __________. Answer: Low. 55. When the balance valve of a non-backdraft instrument leaks, the instrument indicates __________; when the positive pressure side is completely blocked while the negative pressure side remains unobstructed, the instrument indicates __________. Answer: Low, minus 56. The time constant is the time it takes for the output value of the instrument to reach ________% of its stable value when there is a step change in the input. Answer: 63.2 57. The material of K-type thermocouples is __________, and the material of EA-type thermocouples is __________. Answer: Nickel-chromium—Nickel-silicon, Nickel-chromium—Copper. 58. A cascade control system consists of two regulators connected in series, a primary regulator and a secondary regulator; the setpoint of the ______ regulator is automatically adjusted by the primary parameter through the ______ regulator. Answer: Deputy, Main, 59. The necessary conditions for constituting a safe spark-proof explosion protection system are, first, ____________________, and second, _______________. Answer: Use explosion-proof instruments with safe sparks, as well as safety barriers. 60. For control systems, the longer the integration time, the greater the effect______ ； The longer the differentiation time, the more ______ the effect. Answer: Weak Strong 61. The R0 and R100 of a thermocouple thermometer represent the temperatures of ________ and ________ respectively. Answer: 0℃ 100℃ 62. The diaphragm box of a medium differential pressure transmitter is ________ than that of a high differential pressure transmitter, and ________ than that of a low differential pressure transmitter. Answer: Large, Small, 63. A Zener-type safety barrier is composed of ____________, ____________, ____________ etc. Answer: Voltage limiting circuit, current limiting circuit, fuse. 64. When the thermocouple or compensation wire is short-circuited, the instrument indicates…__________ ； It is generally believed that the instrument displays __________ during a short circuit. Answer: Temperature at the short circuit site, room temperature, 65. A simple control system consists of four main components: ____________, ___________, __________, and ____________. Answer: Controlled process, transmitter, regulator, and control valve. 66. The maximum deviation refers to the greatest extent to which the controlled parameter deviates from ___________ during the transition process. Answer: The given value is 67. When measuring the pressure of corrosive media, _________ must be added to prevent corrosion. Answer: Isolation tank. 68. Valve positioners are generally used in situations where the pressure difference before and after the valve is greater than __________, in fluids that contain __________ or are highly viscous, as well as in control valves with a diameter of more than __________. Answer: 10 Kgf/cm2, suspended particles: 100 mm. 69. 1 kilogram-force (Kgf) = __________ Newtons (N); 1 MPa = __________ Kgf/cm2. Answer: 9.8, 10. 70. To measure the current in a circuit, the ammeter must be _________ to that circuit. In order to ensure that the connection of the ammeter does not affect the original state of the circuit, the internal impedance of the ammeter should be as _________ as possible. Answer: Series, small, 71. A proportional-integral controller is suitable for controlling systems in which the channel _________ is small, _________ changes little, and the process parameters do not allow for _________. For example, __________, __________, and demanding level control systems. Answer: Lag, load, tolerance, flow rate, pressure. 72. Replacing a K-type thermocouple with an E-type thermocouple will cause the temperature reading to be __________ than the actual value. Answer: High 73. When stopping the gauge for backflow inspection, the _________ valve should be closed first, followed by the _________ valve. Answer: Once. Backflow: 74. Differential pressure transmitters, classified according to the differential pressure they measure, generally fall into five categories: ______ differential pressure, ______ differential pressure, ______ differential pressure, ______ differential pressure, and ______ differential pressure. Answer: Micro, Low, Medium, High, Large. 75. For a differential pressure transmitter used to measure flow rate, when the positive pressure side is completely blocked while the negative pressure side remains unobstructed, the instrument reading will follow the same trend as the flow rate changes. Answer: On the contrary. 76. The main function of integral control is to eliminate __________. Answer: The residual error is 77. The main function of differential regulation is to eliminate __________. Answer: 78 degrees of lag. The model of the Zener-type safety barrier for thermoresistive outputs is LB______; LB______ type Zener-type safety barriers are used in the output circuit. Answer: 855 840S 79. The value of the instrument’s sensitivity limit should be less than half of the absolute value of __________. Answer: The basic error of the instrument is 80. The amplification factor of the control valve is mainly determined by ____________. Answer: Valve body 81. If the zirconia probe signal is high, then the measurement result will be __________. Answer: Low. 82. Standard throttling devices uniformly use the __________ pressure tapping method. Answer: Corner jointing 83. The regulation laws of regulators include __________, __________, __________, __________, __________. Answer: Two-position control, proportional control, proportional-integral control, proportional-differential control, proportional-integral-differential control. 84. When the control valve is selected as __________, a flow-limiting orifice plate can be added after it. Answer: Large. 85. Control valves can be classified into ____________, ____________, and ____________ based on their source of energy. Answer: Pneumatic control valve, Electric control valve, Hydraulic control valve. 86. The quality indicator for a two-position control process is generally _______________. Answer: Amplitude and period. 87. When using a pressure transducer to measure flow rate, if there is a leak in the valve or pipeline on the positive pressure side, the instrument will indicate ____________. Answer: Low. A cascade control system consists of two regulators connected in series, a primary regulator and a secondary regulator; the setpoint of the ______ regulator is automatically adjusted by the primary parameter through the ______ regulator. Answer: Auxiliary, Main. 89. The necessary conditions for forming a safe spark-proof explosion protection system are, first, ____________________, and second, _______________. Answer: Use explosion-proof instruments with safe sparks, and employ safety barriers. 90. The diaphragm box of a medium differential pressure transmitter is ________ larger than that of a high differential pressure transmitter, and ________ smaller than that of a low differential pressure transmitter. Answer: Large, Small, 91. A Zener-type safety barrier is composed of ____________, ____________, ____________ etc. Answer: Voltage limiting circuit, current limiting circuit, fuse. 92. A hydrostatic level gauge operates based on the principle of balance of fluids ____________; it can be divided into ____________ type and ____________ type. Answer: Static pressure, Pressure, Differential pressure. 93. The presence of the “A” after the model number of a flanged differential pressure transmitter indicates that it can be ____________ migrated ； A “B” indicates that ____________ migration is possible. Answer: Positive Negative 94. The condition for a thermocouple to generate a thermoelectric potential is∶____________ ； ____________ . Answer: The materials of the two thermal electrodes are different; the temperatures at the two contacts are different. 95. The type of regulator in a cascade control system is determined primarily based on ____________, ____________, and ____________. Under normal circumstances, the main circuit usually employs a ____________ or ____________ regulator, while the secondary circuit uses a ____________ or ____________ regulator. Answer: Process requirements, object characteristics, nature of interference – PI, PID, P, PI. 96. Relay contacts come in two types: normally open contacts and normally closed contacts. After the relay coil is energized, its normally open contacts are in the ____________ state, while its normally closed contacts are in the ____________ state. Answer: Closed, Open. 97. The methods to release a relay are ____________, ____________, and ____________. Answer: Direct power cut method, Resistance parallel connection method, Power supply parallel connection method. 98. The reading on an AC voltmeter refers to the ____________ value of the AC voltage. Answer: Valid. The two conditions that must be present for an explosive gas mixture to explode are ____________ and ____________. Answer: A certain concentration, sufficient spark energy. 100. Reducing the shut-off valve connected in series with the control valve will make the adjustable range ____________, while the flow characteristic will become ____________. Answer: Small difference