With Yokogawa Smart Transmitters, it is possible to perform a 4-20 mA trim (i.e. "D to A" calibration). The analog output trim eliminates errors in the transmitter output. For example, if you use the loop test operation to force the transmitter output to 4 mA and the actual transmitter output as measured by a precision ammeter is 3.97 mA, this transmitter output error can be eliminated by performing an analog output trim.