Don Wilhelm wrote:
Certainly components do have a lifetime - and that is expressed in MTBF
- mean time between failures. For most individual components, that time
MTBF is not a measure of lifetime, and ALL components have MTBF's. In
human terms, MTBF is the non-accidental death rate amongst 25 year olds,
which does not predict that hardly anyone reaches 110.
is expressed in hours of power on time - but the lifetime is typically
in the range greater than 100,000 hours (11 1/2 years). Those
If there are more than a couple of components, other than deliberate
consumables, that have an MTBF this low, the design has a serious
reliability problem. E.g. if you have 500 components with MTBFs of
100,000 years, you can expect a failure approximately every 200 hours.
components that fail in a short period of time (usually less than 3
months) are not counted in the MTBF figure and are termed early life
failures. Devices that have operated beyond the early life failure
The failure rate curve that you are referring to is known as the bath
tub curve, because it rises at both the left and right sides. The side
you are referring to is the infant mortality phase, which is often
covered by warrantees, or by factory burn in. However there is also an
old age phase.
In particular, this causes confusion with hard disk drives, as the
system MTBF implies a useful life comparable with human lifetimes, but
old age failure actually sets in at around five years.
--
David Woolley
"The Elecraft list is a forum for the discussion of topics related to
Elecraft products and more general topics related ham radio"
List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm>
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
