Automated torque and resistance measurements of sliding electrical contacts during life testing

A multiplexed accelerated life test system (MALTS) was developed to perform torque and electrical resistance measurements on sliprings as a function of time and rotational speed. The MALTS consists of 30 test fixtures with the associated electronics, all of which are controlled by a single PC. This automation required cost-effective application of state-of-the-art technology in the areas of optical torque measuring devices, high bandwidth-low current milliohm measurements, data acquisition techniques, and high-capacity storage media. In addition to performing precise low-level resistance and torque measurements, it is necessary to control a switching network consisting of 840 relays, independently vary the speed of 30 drive motors, and monitor and control the temperature of all 30 test chambers. Data acquisition parameters such as sampling frequency, data averaging, and resolution are addressed. It is hypothesized that a correlation may exist between electrical measurements for the torque and wear modes so that these measurements could be used as predictors of wear