CCST question

Which of the following is true of most pressure measurement methods?

A. They are not able to measure a small differential pressure.
B. The sensor matches the digital or analog signal conditioning and transmission.
C. They are sensitive to volume but not temperature.
D. They measure pressure by sensing the deflection of the diaphragm.
CCST Answer

The answer is D, “They measure pressure by sensing the deflection of the diaphragm.”

Most pressure measurements are accomplished using a capacitive-type diaphragm sensor. When pressure is applied to the sensor, the diaphragm deflects an amount proportional to the pressure. Capacitive pressure sensors measure pressure by detecting changes in electrical capacitance caused by the movement of this diaphragm. The capacitance measured is inversely proportional to the amount of deflection, so higher pressure = more deflection = higher capacitance. The sensor electronics relates the measured capacitance to the pressure.

Reference: Goettsche, L. D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005. 


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