What does MTBF mean?

MTBF stands for mean time between failures and defines the statistical probability of an accidental device failure.

A variety of different standards, including SN 29500, IEC 61709, MIL HDBK 217 F and Belcore, are used for calculating the MTBF. The calculation always follows the same process. The standard provides a database with the basic failure rates of the individual components. These are then corrected using stress factors from the actual application. The calculated failure rates for all the components are added together to give the failure rate of the complete device.

For example, an MTBF of 1,000,000 hours means that if 1000 devices are in use, statistically a device will fail every 1000 hours. However, it is not possible to say whether a device that has failed was in operation for 50,000 hours or only 100 hours.

The MTBF hours must not be confused with the lifetime hours. PULS provides detailed figures for both properties in its product datasheets.