Contact resistance effects in mechanical choppers

The contact resistance of a mechanical chopper is affected by several factors including, in particular, the type of contact material, the amount of sliding action between the contacts, and the local atmospheric environment. The paper discusses the results of tests involving more than 200 choppers of a particular design, in which these factors were varied. A high degree of reliability was obtained when contacts of suitable materials were operated with a slight degree of sliding and the choppers were free to breathe. Hermetic sealing was found to promote the growth of contact resistance.