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.
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:
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:
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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