1. INTRODUCTION 1 2. BACKGROUND. 3. MULTIMETER OPERATING PRINCIPLES AND APPLICATIONS 3.1. Basic Modern Digital Multimeter Design 3.1.1. DC Voltage Measurements 3.1.2. AC Voltage Measurements 3.1.3. Resistance Measurements 3.1.4. Current Measurements 3.1.5.
a test setup. Ground currents can slow the settling time of voltage steps applied to a test circuit or the output voltage to be measured. ACKNOWLEDGMENT The author wishes to thank B. A. Bell and T. M. Souders of the Electrosystems Division, NBS, for their very helpful suggestions in preparing this manuscript.
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.
Hands-Free Communication Systems (HFCS) are used by law enforcement agencies, fire departments, rescue squads, and the Armed Forces, where tasks require the communications operator's hands to be free.Four such HFCSs were tested to measure their operational characteristics of voltage gain/frequency response, signal-to-noise ratio, total harmonic distortion, and sensitivity.
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