Tutorial 7
Keysight 34970A/34972A User’s Guide 337
Relay Life and Preventive Maintenance
The 34970A/34972A Relay Maintenance System automatically counts the cycles
on each relay in the instrument and stores the total count in non-volatile memory
on each switch module. Use this feature to track relay failures and predict system
maintenance requirements. For more information on using this feature, refer to
“Relay Cycle Count” on page 177.
Relays are electromechanical devices which are subject to wear-out failure
modes. The life of a relay, or the number of actual operations before failure, is
dependent upon how it is used – applied load, switching frequency, and
environment.
You can use the graphs shown in this section to estimate relay lifetimes for your
application. Additional background information is also provided to give you a
better understanding of relay wear-out mechanisms. In general, relay lifetimes
depend heavily upon the signals that are being switched and the types of
measurements being performed.
– Switching typical signal levels will result in relay lifetimes from 1,000,000 to
10,000,000 operations.
– High-power switching (>25% rating) or high-voltage switching (>100V)
applications will yield relay lifetimes from 100,000 to 1,000,000 operations.
– Low-voltage switching (<30V) and low-current switching (<10 mA)
applications will yield relay lifetimes to 10,000,000 operations.
– RF switching applications seldom exhibit relay lifetimes exceeding 1,000,000
operations due to more stringent contact resistance requirements (typically
less than 0.2Ω).
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
1 / Minute
1 / Second
10 / Second
12 Years
10 Weeks
1 Day
3 Hours
2 Years
12 Days
1 Day
4 Months
12 Days
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