【2025 Knowledge Accumulation】Questions 7–9 with Answers
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This post was last edited by The one on 2025-11-27 11:21. 7. When a mass flow meter is used to measure gas flow, what effect does it have on the measurement results if the operating pressure is much lower than the calibration pressure? A. The indicator value is high. B. The indicator value is low. C. The indicator value remains unchanged. D. The indicator value fluctuates. Answer: B. Reason: A mass flow meter measures mass flow rate. When the gas pressure decreases, the gas density decreases. At the same mass flow rate, the actual volume flow rate increases, but the flow velocity sensor may still calculate based on the original density, resulting in a lower displayed mass flow rate. Therefore, in gas measurement, pressure compensation is necessary when required.
8. In which of the following operating conditions does an ultrasonic level gauge achieve the best measurement results? A. A liquid surface with a large amount of foam B. A container with frequent pressure fluctuations C. A calm liquid surface without dust D. A medium with very high viscosity. Answer: C. Reason: An ultrasonic level gauge operates by relying on the reflection of sound waves at the surface of the medium. A calm liquid surface and a dust-free environment can provide stable and clear echo signals, representing the ideal operating conditions for ultrasonic level gauges. Foam absorbs sound waves, pressure changes affect the speed of sound, dust attenuates signals, and viscosity influences the shape of the beam.
9. In a fuel gas pressure control circuit, to ensure that the fuel gas is cut off in the event of a failure in the instrument air supply and to prevent the furnace temperature from rising too high, what should be used? A. Air-open control valve B. Air-close control valve C. Double-acting control valve D. Electric control valve Answer: A Reasoning: This is a typical application of the fail-safe principle. In the event of a failure in the instrument air supply (loss of air), the valve must be in the closed (FC) position to cut off the fuel and ensure safety. Therefore, it should be open when the air supply signal is normal, that is, an air-to-open valve.
Below are the links to Siemens selection software for reference. (1) TIA_Selection_Tool_cloud (online cloud version) https://mall.industry.siemens.com/tst/#/Start
(2) TIA_Selection_Tool (offline standalone version) link: https://pan.baidu.com/s/1RnNeuZwyPdHaYUBT8aGrVA Extraction code: 1111
(3) TIA_Selection_Tool tutorial link: https://pan.baidu.com/s/1SJMVlsJUqrNDWdtkssMHHQ Extraction code: 1111
(4) SIZER_V3.23 link: https://pan.baidu.com/s/1AC8dygWdfic8gqyACwbNPg Extraction code: 1111
(5) SIZER_V3.22 link: https://pan.baidu.com/s/1iFh9tnFqNskmLayP2P87qw Extraction code: 1111
(6) SIZER_V3.21 link: https://pan.baidu.com/s/1qlA2R4FMKoZGzHzOxpihPQ Extraction code: 1111
(7) SIZER_V3.20 link: https://pan.baidu.com/s/1rn8W4Zkr2G3t_Io9u3nKXA Extraction code: 1111
(8) SIZER_V3.19 link: https://pan.baidu.com/s/1bOkJLZR5kx_nsgfJ5Ht2Mg Extraction code: 1111