Application Notes

EAP-032112

Remote Ratio Setting for MV Signal

We have a 4-20 mA manipulate signal. And we also have a potentiometer on the panel with resistance range 0-1k ohm. Adjusting this pot. we’d like to get multiplied output with the ratio 0.5 to 1.5.

Please advise how we should do with 4-20mA and potentiometer value?

We believe that the combination use of Potentiometer Transmitter (model: M2MS) and Two-input Math Function Module (model: FJF) would meet your request.

Please connect the manipulate 4-20 mA signal to the FJF’s input 1 (terminal 1 & 2). On the other hand, please use the M2MS and convert the potentiometer value (0-1k ohm) to proportional 4-20 mAdc and then put this 4-20 mA to the FJF’s input 2 (terminal 3 & 4).

On the FJF, please select the equation code as multiplication (suffix code /4) and specify each parameter as gain 1 for each of K0, K1 and K2 and as bias 0% for A1 and 50% for A2.

EQUATION: X0 = K0 (K1X1 + A1)(K2X2 + A2) + A0

<parameters>
X0=output (%)
X1 to X2 = input (%)
K0 to K2 = gain
A0 to A2 = bias (%)

With above connection, you can get requested output, which is multiplied operational 4-20 mA and potentiometer manual value with the ratio 0.5 to 1.5.