Calculate Flow Transmitter Output Current

A  flow transmitter  is  ranged  0  to  350  GPM,   4-20  mA  output,   direct-responding. Calculate  the current signal value at a flow rate  of 204 GPM.

We are solving this problem using standard 4-20mA conversion Formula. Click here for formula

One  way  we could  solve for the amount  of signal  current  is to convert  the flow value  of 204 .

GPM  into a ratio of the flowmeter’s full-flow value,  then apply  the same  formula  we used  in the previous example relating percentage to milliamps.  Converting the flow rate into a “per unit” ratio is a matter of simple division, since the flow measurement range is zero-based:

Therefore,  the transmitter should output a PV signal of 13.3 mA at a flow rate of 204 GPM.

An alternative approach is to set  up  a linear  equation specifically for this flowmeter  given its measurement range (0 to 350 GPM)  and output signal range (4 to 20 mA). We will begin this process by sketching  a simple graph  relating flow rate to current:

Therefore,  the transmitter should output a PV signal of 13.3 mA at a flow rate of 204 GPM.

We can also solve the problem using direct formula. Click here for formula

Also Read: Instrumentation Formulas

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