Relay life tests with contact resistance measurement after each operation

Modern reliability requirements for relays cannot be satisfied unless the contact resistance is measured after each operation of the life test. A test device was developed to execute these measurements and a special method was applied to reduce the resulting amount of data effectively without losing information. Commercial relays were investigated at intermediate and low power levels. Characteristic contact resistance patterns during the total life of a relay were recorded depending on both the contact material and the electrical stress. Typical statistical patterns characterizing the behavior of homogeneous materials (Au, Ag/Ni 0.15) and heterogeneous materials (Ag/CdO, Ag/SnO₂), erosion of contact platings, contact contamination, and the behavior of bifurcated contacts were recognized