Abstract: A self-contained hand-held portable pocket probe for trouble shooting direct current electrical systems. The probe includes an electrically conductive probe, a ground terminal, and first and second electrical circuits connected in parallel between the probe and ground terminal. The first electrical circuit includes an illumination device, a rectifying device, and a device for limiting current flow through the illumination device. The first electrical circuit normally enables positive current flow only in the direction from the probe to the ground terminal. The second electrical circuit normally allows current flow in a direction from the ground terminal to the probe and includes an illumination device, a rectifying device and a battery. The probe is designed for use with direct current systems having maximum test voltages in the range of 6-24 volts and for measurement of low impedance grounds.

Abstract: An improved electronic DC test probe particularly suitable for rapidly and flexibly trouble shooting automotive electrical systems. The test probe features highly reliable electronic circuits energized from an automotive battery through a pair of connector members suitable for connection to the terminals of the battery. A conductive test prod and a pair of indicator lamps are housed within a hand-held probe housing and enable an operator to rapidly trouble shoot the entire electrical system without alteration of any kind to the battery terminal connections. Electronic reference voltage establishing circuits protect the probe circuits and extend the operative life of the indicator lamps. The normally extinguished indicator lamps are illuminated only during actual test measurements with an intensity that varies proportionately with the measured signal.