A Venturi meter determines fluid flow velocity by measuring a pressure differenc

Question

A Venturi meter determines fluid flow velocity by measuring a pressure difference. This can be done using two independantpressure sensors, P1 and P2, or a single pressure transducer that measures the pressure differential directly, DP = P1-P2. The venturi formula is given as:

w = K*(P1-P2)0.5

Assume that K is a known constant and P1=4 psi, P2=3 psi, and DP=1 psi. Assume that these are measured with a relative uncertainty (e.g. 10% uncertainty is up1 = 0.1*P1). Which of the following will result in the least flow measurement uncertainty.

a) Using two independent pressure sensors with 2% uncertainty.

b) Using a single differential pressure sensor with 10% uncertainty.

c) Neither. Both options result in equal uncertainty.

a) Using two independent pressure sensors with 2% uncertainty.

b) Using a single differential pressure sensor with 10% uncertainty.

c) Neither. Both options result in equal uncertainty.

Explanation / Answer

The venturi formula is given as:

w = K*(P1-P2)0.5

As the uncertainity is independent of number of sensors being used,

Both options result in equal uncertainty. (c) is Correct.

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