Model PM-4A is a true RM ammeter which uses an integrated circuit to compute the true RMS value of complex waveforms. A 0-5A input from a current transformer (CT) is fed into the ammeter. By dialing the user-selectable CT ratio switch setting into the meter, the microprocessor then processes this input and translates it into true current. The results are sent to and then read from the four digit LED display. The PM4-A is used with 5:5 to 1500:5 current transformers and with standard 115, 230, or 460VAC power supplies. The PM4-A has a 10 sample per second conversion rate and less than 0.25 second full range step response. The decimal point is automatically positioned on the PM4-A and the displayed resolution changes with the changing decimal point position.