Characteristics of the A.S.T.M. Testing Method for Electrical Contact Materials and its Modification

Abstract

In the course of developing new series of contact materials, a standard testing apparatus was constructed after ASTM B-182-49. Using pure silver contact, measurement were made on the number of welds formed, contact resistance, temperature rise and weight loss during and after a series of make-and-break cycles.
It was found that the tendency of electrical contacts to weld was affected by various factors characteristic of the testing apparatus, i.e., closing and opening speeds of contacts, vibration of the apparatus and chattering of contacts, the latter being markedly influenced by the closing force and momentum of the moving arm.
For these and other reasons, a modified apparatus was constructed using photo-transistors and obtained a much more satisfactory results than the standard one.