Relay Life

NI Switches Help

Edition Date: April 2015

Part Number: 375472H-01

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NI switches typically specify a conservative estimation of the expected life of the electromechanical relay components. Relay life is specified as a minimum number of cycles before the end of the relay life. One cycle is defined as the action of opening and closing the relay. The expected life is divided into two main categories: mechanical and electrical life.

Tip  Some switch modules are capable of tracking relay usage using the niSwitch Get Relay Count VI or the niSwitch_GetRelayCount function. Refer to Relay Count for more information.

Mechanical Life

The contacts of mechanical relays wear with usage, and worn contacts have a higher contact resistance. The mechanical life specification is typically the number of switch cycles before the contact resistance rises above 1 Ω. This rating assumes no electrical load across contacts during actuation.

Electrical Life

Switching active electrical signals, especially high power signals, causes arcing across the relay contacts. This arcing produces pits on the contact surface and accelerates the contact wear described in Mechanical Life. The electrical life specification is the number of switch cycles, under load, before the contact resistance rises above 1 Ω.

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