The following table shows the time required to reach the specified number of switch operations for several
switching speeds.
Continuous switching speed Switching operations
100,000 1,000,000 10,000,000
1 / hour 12 years N/A N/A
1 / minute 10 weeks 2 years N/A
1 / second 1 day 12 days 4 months
10 / second 3 hours 1 day 12 days
Relay Life
As a relay is used, the contacts begin to wear and the resistance of the closed contacts increases. The initial
contact resistance of a relay is typically 50 mΩ (plus lead resistance). When the contact resistance exceeds
20 to 50 times its initial value, the contact resistance becomes very erratic and the relay should probably be
replaced. For most applications, a relay with contact resistance greater than 1 Ω should be replaced. The
graph below shows the typical contact resistance characteristics of the relays used on the DAQ970A switch-
ing modules.
Relay Load
For most applications, the load switched by the relay is the most important factor affecting relay life. As
shown in the graph below, relay life is maximized by switching low power. As the power switched increases,
relay life deteriorates.
4Measurement Tutorials
230 Keysight DAQ970A User's Guide
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