An Open-Lead Detection Voltmeter Circuit

A novel voltmeter design that can automatically detect open leads.

Abstract

This paper documents a voltmeter design that allows the detection of open leads, allowing the meter to distinguish between when a "zero volts" reading indicates "these point are on the same net" or "current is not attempting to flow and can not flow between these two points." This detection is done without relays and from behind the protective high-impedance voltmeter input circuitry, making it safer and faster than taking a continuity reading by switching modes. This paper shows the schematic and discusses variations on the circuit for different use cases.