MTBF

MTBF (engl. for“Mean Time Between Failure“) is the statistical probability of a “random device failure”.
Various standards such as SN 29500, IEC 61709, MIL HDBK 217 F, Belcore and others are available for calculating the MTBF value. The calculation always follows the same pattern. The standard provides a database with basic error rates of the individual components, which are then corrected with the stress factors from the actual application. The calculated error rates of all components are added together to give the error rate of the entire device.
An MTBF figure of 1,000,000 hours, for example, means that if 1,000 devices are used, statistically one device will fail every 1,000 hours. However, it is not possible to say whether a failed appliance has been in use for 50,000 hours or just 100 hours. The MTBF hours must not be confused with the service life hours.