Example of 3-15 psi to 4-20mA Conversion

A current-to-pressure transducer is  used  to  convert  a  4-20 mA  electronic  signal  into  a  3-15 PSI pneumatic signal.

This particular transducer is configured  for  reverse action instead  of direct, meaning that its pressure output at 4 mA should be 15 PSI  and its pressure  output  at 20 mA should be 3 PSI.

Calculate the necessary current signal value to produce  an output  pressure  of 12.7 PSI.

3-15 psi to 4-20mA Conversion

3-15 psi to 4-20mA Conversion

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

Reverse-acting  instruments  are  still  linear,  and  therefore  still  follow the slope-intercept  line formula y = mx + b, albeit with a negative slope:

3-15 psi to 4-20mA

Calculating and substituting the slope (m)  value for this equation, using the full rise-over-run  of the linear function.

Note how the “rise” is actually  a “fall” from 20 milliamps  down to 4 milliamps, yielding a negative value for m:

Formula 3-15 psi to 4-20mA Conversion

Therefore,  a current signal of 7.07 mA is necessary to drive the output of this reverse-acting I/P transducer to a pressure  of 12.7 PSI.

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10 thoughts on “Example of 3-15 psi to 4-20mA Conversion”

  1. Hello Sir,
    I am facing a problem as you provided formula,if it’s any mistake from my side please correct me.
    My question is 15 PSI should be 20MA
    Hence =(-16÷12)= -1.3333
    =(-1.3333×15PSI)= -19.9999
    =(-19.9999)+24= 4.0 MA
    Why I get 4MA?
    If any mistake please correct me



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