True RMS Ammeter Calibration by Using Standard Square Waveform Signal and Algorithm for Measurement and Processing of Results

A computer-based system and algorithm for calibration of True RMS ammeters is proposed. An approach was used to calibrate True RMS ammeters by using standard square waveform signals as an alternative of the classical used harmonic signal. Based on a developed algorithm, the calibration system performs the sequence of steps for controlling the Metrix CX1651 standard calibrator and the calibrated True RMS ammeter PICOTEST M3500A. For this purpose, standard True RMS current values from the calibrator are set, multiple measurements are made at the calibration point, measured results from the ammeter are derived and processed to receive an estimate of the actual value of the measured current values and an estimate of the expanded uncertainty at the calibration point. Results of calibrations using classic sinusoidal and square waveform signals were received, and the two approaches were compared and analyzed, which evidenced their equivalence.