A System for Analyzing Contact Resistance

A resistance measuring system and technique which has proven to be valuable as a means for studying the resistance behavior of electrical contacts is described. The system described is not intended for the rapid repetititive collection of resistance data but rather for gaining insight into the conduction properties of a contact by providing a versatile measurement system which takes into account the various quantities which affect contact resistance. The main feature of this system, known as the contact resistance analyzer, is the graphical display of resistance information in the form of voltage-current characteristics which cover a wide dynamic resistance range on one plot. Other graphical information is available in the form of resistance versus force curves and resistance as a function of other variables such as time and temperature. In addition, digital readout of resistance is provided. The system is capable of examining the resistance of actual components or of discrete metallic surfaces including measurements of the crossedrod, probe-coupon, or probe-component types. In all cases measurements are made with separate voltage and current leads arranged in the conventional four-wire configuration to minimize the inclusion of bulk resistance into the measurements. The contact resistance analyzer has found wide applications in studies which include resistance behavior with regard to constriction resistance, lubrication, flux contamination, and environmental tests for relay contacts, switches, separable connectors, and other metallic surfaces. The results of several selected studies which illustrate particular resistance behavior are described.