How to Calibrate the Active and Reactive Power Transducer

Twiddle the knob on a known load! You'll get there in the end

A typical transducer will have mini trim potentiometers for calibration. There are usually two of them (span, which adjusts the relative range between maximum and minimum output, and zero, which adjusts the absolute value of the minimum). They are usually accessed through little holes in the transducer case, using a tiny screwdriver. Sometimes the holes will have a plug in them or a label over them, or (less likely) the cover of the transducer needs to be removed.

You have to provide a known, calibrated source of power, so that you are certain of the value going in (amps, volts, frequency, phase angle), and a calibrated meter to read the output (0-1 or 4-20 milliamps, etc.). If you don't have these, then your calibration of the transducer is meaningless. Adjustment of the zero and span can affect each other, so you will need to check one, adjust, check the other, adjust, and go back over again a few times if the calibration begins out of spec.