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Chapter 8 Tutorial
Relay Life and Preventative Maintenance
Relay Life and Preventative Maintenance
The HP 34970A 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 147.
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 0.2 .
The following table shows the time required to reach the specified number
of switch operations for several switching speeds.
Continuous
Switching Speed
100,000
1 / Hour
12 Years
1 / Minute
10 Weeks
1 / Second
1 Day
10 / Second
3 Hours
Switch Operations
1,000,000
10,000,000
2 Years
12 Days
4 Months
1 Day
12 Days
8
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