Switching Frequency
Relay contacts heat up as they switch significant power. The heat is dissipated through the leads and the
body of the relay. As you increase the switching frequency to near its maximum, heat cannot dissipate
before the next cycle. The contact temperature rises and the life of the relay is reduced.
Replacement Strategy
There are essentially two strategies that you can use for preventive maintenance of the relays on the
switching modules. The strategy that you choose depends upon your application, the consequences
of a relay failure in your system, and the number of relay cycles during a measurement session.
The first strategy is to replace each relay as needed after it fails or becomes erratic. This is suitable if
you are switching higher loads on only a few relays on the module. The disadvantage of this strategy is
the inconvenience of continually replacing relays as they near the end of their life at different times.
The second strategy is to replace all relays on the module or simply purchase a new module as the
relays near the end of their life. This strategy is best suited for those applications where all relays on
the module are switching similar loads. The failure of several relays over a relatively short period of
time may indicate impending failures on other relays switching similar loads. This strategy decreases
the risk of failure during actual use at the expense of replacing some relays that may have useful life
remaining.
For switching frequency and replacement strategy as described above, you can use the DAQ970A
Relay Maintenance System to track and even predict relay failures.
Keysight DAQ970A User's Guide 231
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