A fast response, low-frequency sampling voltmeter

Abstract

A low-frequency voltmeter utilizing a sampling technique implemented with microprocessor-based electronics has been developed to perform as a true rms ac voltmeter and distortion analyzer. The instrument makes measurements accurate to ±0.1 percent (of reading) of the fundamental frequency, total harmonic distortion, and true rms voltage of approximately sinusoidal inputs from 2 mV to 10 V and frequencies from 0.1 to 120 Hz. A major feature of this instrument is the special window crossing and error function algorithms which provide a software means for completing a measurement within two signal periods at frequencies below 10 Hz.

Standards for waveform metrology based on digital techniques

“…The speed and versatility that is possible with digital waveform sampling of low-frequency ac waveforms was demonstrated with the development of the NIST Low-Frequency ac Sampling Voltmeter [ 35 ]. An rms low-frequency (0.1 to 50 Hz) voltmeter/calibrator had been developed at NIST about the same time, and employed a multi-junction thermal converter device for making accurate rms-to-dc conversions.…”