MTBF, MTTF interpretation
MTBF, MTTF interpretation
(OP)
Looking at MTTF and MTBF data, if the MTTF of a device is 20,000 hrs (say 100 devices are tested)does that mean we should expect one device to fail after 20,000 hrs out of a population of 100 or that the expected life of any individual it 20,000 hrs?





RE: MTBF, MTTF interpretation
RE: MTBF, MTTF interpretation
RE: MTBF, MTTF interpretation
Section 8 of MIL-HDBK-338 discusses the theory in some detail.
TTFN
RE: MTBF, MTTF interpretation
By the way, there's always confusion between MTTF and MTBF. Mean Time To Failure is used for non-repairable devices like components/integrated circuits and is the inverse of the failure rate (FIT). Mean Time Between Failures is used for "repairable" devices, which include assemblies like systems, disk drives, etc. They're calculated essentially the same way.
Here's a good tutorial on component failure rate calculation:
http://www.odyseus.nildram.co.uk/Compone...
Be careful taking this stuff and these numbers at face values. It's important to understand thermal activiation energies, temperature acceleration factors, voltage acceleration factors, node coverage during life test, and so on to really be able to understand the relevance of a given MTTF to your situation.
Mike
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Mike Kirschner
Design Chain Associates, LLC
http://www.designchainassociates.com