How is an orifice-plate flowmeter measurement in a flow control loop affected by an increase in fluid density?
A. Decreases flow measurement linearly with fluid density
B. Decreases flow measurement as square of fluid density
C. Decreases flow measurement as the inverse square root of fluid density
D. None of the above
The output of a differential-pressure transmitter (Q) is proportional to the square root of the ratio of the differential pressure (ΔP) to the fluid density (ρ).
Q α ( ΔP / ρ ) ½
The flow control loop maintains the output of the differential-pressure transmitter constant, so ΔP remains constant. Fluid density is in the denominator and within the square root, so increasing fluid density will decrease the flow measurement as the inverse of the square root of fluid density. Answer C is correct.Additional Complicating Factors
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