Constriction resistance measuring system for residential branch circuit connections

A constriction resistance measuring system was designed for evaluating the performance of residential branch wiring circuit connections. The measurement system separates the bulk from the constriction resistance by utilizing the nonlinear voltage‐current behavior of a connection. The method overcomes some of the past problems with the nonlinear technique by employing a pulse stimulus current coupled to a high‐speed data acquisition system under computer control. A least squares nonlinear fit program is used to obtain the best fit of the voltage‐current data to an equation which serves as the nonlinear model. The model was verified by simulating connections with a ’’true 4‐wire crossed rod’’ measurement technique. Measurements on connections formed with aluminium and copper conductors agree closely with the parameters predicted by the model. The method is shown to have the ability to accurately measure the constriction resistance of practical connectors in the presence of widely changing values of bulk resistance. A modification of the technique is proposed and shown to have a potential threefold increase in sensitivity.