On Mon, 12 Sep 2016 14:04:21 GMT, (Scott Lurndal)
wrote:

T writes:
On 09/10/2016 12:41 PM, Ed Pawlowski wrote:
tolerance for MTBF

Hi Ed,

That is not what MBTF means. If the bulb had, say 1000 hour
MBTF, it would mean that you put 1000 bulbs in a test bench
and ran them for an hour. Only one failed. MBTF does not
tell you anything about the second and so forth hours.
(I did MBTF analysis for the military.)

Yet, you can't even spell the acronym correctly.

MTBF - Mean Time Between Failures

"The predicted elapsed time betwen inherent failures of a system
during operation".

Of course, in a system that can't be repaired, such as an LED
A19 bulb, the proper acronym is MTTF (Mean Time To Failure).

Note that it is incorrect to extrapolate MTBF to give an estimate
of the life time of a component, because of the much higher failure
rate during end-of-life.

Note also the first term is 'Mean', which implies failures on
either side of the computed MTBF can be expected.
Actually the highest failure rate per unit time is when the product
is new. "infant mortality" is a bigger issue than "old age".

I guess technically you are mabee correct, because just before they
fail - at whatever age, they are "approachiung end-of-life"

Predicting "end of life" becomes the issue. We had all kinds of
trouble with LED MR16 or GU10 (whichever the 12 volt ones are) so we
went back to halogens - these are in a 14-20 foot mceiling. They have
been in a month now, and already 3 out of 54? are dead.......