An Instrument for Finding the Maximum RMS Current/Voltage Application: Ringing and Tone Systems

This paper describes a microcomputer controlled current and voltage measuring instrument which was primarily designed to find the maximum rms current in selectable time intervals of 1, 5, 15 or 60 minutes, or an indefinitely long interval. The instrument consists of a Measurement Controller (MC), which is the main subject of the paper, up to three current probes, associated amplifiers, and a small printer. The MC and current probe amplifiers plug into a portable power module which is about the size of a small suitcase. The MC has a 3 1/2 digit display that is updated every 200 milliseconds. The instrument can also be used as a continuous indicating true rms ammeter or voltmeter. The usable frequency range is dc and 15 Hz to 2500 Hz.