Reed Relays and
Electronics India Limited
Manufacturer of Reed Switches, Reed Sensors and Reed-based products
Reed Relays and Electronics India Limited Incorporated in 1971

Contact Resistance [CR]

Contact Resistance  measured in milli-ohms, is the electrical resistance of a reed contact in closed state, as measured terminal to terminal, at their associated terminals. This is usually measured with a coil at 25% overdrive. Four-terminal Sensing and shielded cables should be used for accurate contact resistance measurements.

Contact_resistance (Wikipedia)

The term contact resistance refers to the contribution to the total resistance of a system which can be attributed to the contacting interfaces of electrical leads and connections as opposed to the intrinsic resistance. This effect is described by the term electrical contact resistance (ECR) and arises as the result of the limited areas of true contact at an interface and the presence of resistive surface films or oxide layers. ECR may vary with time, most often decreasing, in a process known as resistance creep. The idea of potential drop on the injection electrode was introduced by William Shockley to explain the difference between the experimental results and the model of gradual channel approximation. In addition to the term ECR, interface resistance, transitional resistance, or just simply correction term are also used. The term parasitic resistance is used as a more general term, of which it is usually assumed that contact resistance is a major component.

Sketch of the contact resistance estimation by the transmission line method.
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