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General-purpose Relay: What is Failure Rate?

FAQ No. FAQ02147

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What is a failure rate?


A failure rate expresses a rough guide to the switchable limits of electronic circuits and other very small loads (i.e., microloads).

The percentage of failures per unit time during continuous relay switching (number of operations) under individually specified test types and loads. The failure rate will change depending on the switching frequency, the environmental conditions, and the expected reliability level. Failure rates must always be checked on equipment under real operating conditions.

The failure rate is listed as the P level (reference value). This expresses the failure level at a reliability level of 60% (λ60) (JIS C5003).

LevelFailure rate (/operation)
L5 × 10-6
M1 × 10-6
N0.5 × 10-6
P0.1 × 10-6
Q0.05 × 10-6

λ60 = 0.1 × 10-6/operation means that 1/10,000,000 failures can be expected at a reliability level of 60%.