Reed Relay Protection

NI Switches Help

Edition Date: April 2015

Part Number: 375472H-01

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The life expectancy of a reed relay can be greatly affected by the nature of the load. To prolong the life of reed relays, consider the following list when using switches with reed relays:

• Bounce
• Arcing
• Inrush Current
• Switching Capacitive Loads
• Board Layout and Topology
• Example System

In general, reed relays are vulnerable to contact welding from high currents. Parasitic capacitance within a system can unavoidably create high inrush currents that can damage the reed relay. To minimize inrush current, decrease or isolate external capacitance by:

1. Using lower switching voltages.
2. Avoiding large capacitive loads to the switch.
3. Isolating external capacitance with series impedance R_p such that:

V/R_p< switching current rating of the relay