Having worked at a large electronics manufacturer, the initial MTBF
calculations are a roll-up of all the components MTBFs from the
component manufacturers. Yes it is calculated. Do you take it as gospel?
I don't think so.
bp
<part15sbs{at}gmail{dot}com>
On 8/26/2017 11:31 AM, Kurt Fankhauser wrote:
So does anyone actually think that a radio manufacturer took 100
radios off the shelf and tested them simultaneous to calculate out
some average and derive at the number they state? I highly doubt that
many radios were tested especially considering the cost of some of
these radios!!!
On Sat, Aug 26, 2017 at 2:03 PM, Forrest Christian (List Account)
<[email protected] <mailto:[email protected]>> wrote:
Need to correct my example:
10 devices fail in the first year. 10% per year. 50% would be at
5 years. So the MTBF is 5 years. Adam's explanation is likely
also accurate.
On Sat, Aug 26, 2017 at 12:01 PM, Forrest Christian (List Account)
<[email protected] <mailto:[email protected]>> wrote:
My understanding is that MTBF is usually calculated by taking
a certain sample size, then seeing how many fail over a
certain amount of time. From this number you can then use
statistics to determine how many years the rest will last.
A simplified example would be if you take 100 devices, and 10
fail in the first year, then you assume that 5 would fail per
year, and the mtbf would be 5 years.
Remember 'M' is mean. Or average. Which roughly means that
only half of the units will still be working in that amount of
time. It doesn't mean your particular radio will last that
long, just that half of the radios will last that long. Yours
might fail in 10 days or a year or never....
Personally, I believe that this method is rather dubious since
some electronic parts exhibit wear-out. Electrolytic
capacitors as an example. Even if very few devices fail at 5
years, there is a good chance that most will fail at 20 years
after the electrolytic caps have dried out.
On Sat, Aug 26, 2017 at 9:29 AM, Kurt Fankhauser
<[email protected] <mailto:[email protected]>>
wrote:
Where do these MTBF ratings come from by radio
manufacturers? Are they just made up numbers the
manufacturer "hopes" that the product can achieve or is
actual testing done to get to these numbers? I thought i
seen a radio once with a 90 year MTBF rating. How they
hell can they determine that? The components in the radio
didn't even exist 90 years ago.
If a radio manufacture states in the spec sheets that the
radio has a 40 year MTBF rating but then also admits that
after 4 years expect to have problems due to a design
flaw, what does that mean? Is the expected MTBF rating
only good in a "lab environment" under "ideal conditions"?
Seems to me the MTBF is just marketing fluff and actually
doesn't mean crap....
--
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Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
[email protected] <mailto:[email protected]> |
http://www.packetflux.com <http://www.packetflux.com/>
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