MTBF criteria was developed by the military to predict life expectancy/reliability for electronic equipment and as such use certain values for component failure rates. These component values are often misleading when applied to industrial/commercial electronics due to the large diversity of applications. This is particularly true in the case of solid-state relays and I/O modules. Actual applications of the products alter the MTBF calculations significantly. e.g.: Power dissipation of modules can be significantly different in the on-state versus the off-state; Duty cycle can vary from 1% to 100%, ect.

Crouzet does not publish specific MTBF figures for its modules due to the varied nature of applications. However, a range of MTBF figures, that is worst case to best case, can be estimated by theoretical means:

Best case is around 40 million HRS
Worst case is around 2 million HRS

Field data suggest these figures are pessimistic. Actual PPM rates are typically less than 50 PPM depending on hours of service. Actual MTBF can be greater than 2 million HRS