calculate MTBF
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From: Phil Hobbs on 21 Jan 2010 20:19 On 1/21/2010 10:24 AM, Rich Webb wrote: > On Thu, 21 Jan 2010 15:06:10 +0000, Raveninghorde > <raveninghorde(a)invalid> wrote: > >> >> How do you calculate MTBF? > > For a component? For an entire system? 217 or Bellcore/Telcordia or ... > > The Wikipedia article isn't a bad place to start. If you're tasked with > doing a full-up parts-stress reliability prediction analysis, good luck! > 217? <shudder> Who said there was no such thing as a true random number generating algorithm? Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs at electrooptical dot net http://electrooptical.net
From: John Larkin on 21 Jan 2010 20:33 On Thu, 21 Jan 2010 20:19:32 -0500, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >On 1/21/2010 10:24 AM, Rich Webb wrote: >> On Thu, 21 Jan 2010 15:06:10 +0000, Raveninghorde >> <raveninghorde(a)invalid> wrote: >> >>> >>> How do you calculate MTBF? >> >> For a component? For an entire system? 217 or Bellcore/Telcordia or ... >> >> The Wikipedia article isn't a bad place to start. If you're tasked with >> doing a full-up parts-stress reliability prediction analysis, good luck! >> > >217? > ><shudder> > >Who said there was no such thing as a true random number generating >algorithm? > >Cheers > >Phil Hobbs We use Bellcore because the calculated MTBFs come out much higher. John
From: Artemus on 21 Jan 2010 20:54 "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message > > We use Bellcore because the calculated MTBFs come out much higher. > > John > It's been a long time since I did any of that stuff but IIRC the MIL calcs used 125�C for the high temp and Bellcore used 85�C. This would account for the better numbers. Art
From: mook johnson on 21 Jan 2010 21:35 "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:rhahl5t756021nl1ld64dtmo0ei4paqskt(a)4ax.com... > On Thu, 21 Jan 2010 12:43:20 -0500, Rich Webb > <bbew.ar(a)mapson.nozirev.ten> wrote: > >>On Thu, 21 Jan 2010 16:35:55 +0000, Raveninghorde >><raveninghorde(a)invalid> wrote: >> >>>On Thu, 21 Jan 2010 07:33:02 -0800, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>On Thu, 21 Jan 2010 15:06:10 +0000, Raveninghorde >>>><raveninghorde(a)invalid> wrote: >>>> >>>>> >>>>>How do you calculate MTBF? >>>> >>>>Get the failure rate of each part (specified in FITS, failures per >>>>billion hours), add them up, take the reciprocal, multiply by a >>>>billion. >>>> >>>>John >>> >>>Thanks >>> >>>The National site is good and I found the info for the their parts. >>> >>>Microchip no luck, IR no luck. So where do you normally find the >>>information? >>> >>>I suppose one also assumes perfect ESD procedures, and perfect lead >>>free soldering. >> >>You're new at this so, even if you're not doing a MIL-STD prediction, >>I'd strongly recommend downloading MIL-HDBK-217 from the online site >><https://assist.daps.dla.mil/quicksearch/> (search on MIL-HDBK-217 in >>the Document ID field) and skimming though sections 3 and 4. The >>Bellcore process is similar. >> >>John's basic equation is correct. You can use the tables in 217 to >>estimate the reliability of items for which the manufacturer does not >>provide the info. > > One reason we paid for the Bellcore TR-332 document is that their > numbers are much better. I assume it's the difference between > commercial and military applications. > > John the First paragraph in the 217 states that the analysis results cannot be used for contractual requirements. The MTBF numbers calculated are only for a guidance. Try telling that to managment once they get that MTBF number in their hot little hands. :)
From: Robert Baer on 22 Jan 2010 05:02
Raveninghorde wrote: > On Thu, 21 Jan 2010 10:24:29 -0500, Rich Webb > <bbew.ar(a)mapson.nozirev.ten> wrote: > >> On Thu, 21 Jan 2010 15:06:10 +0000, Raveninghorde >> <raveninghorde(a)invalid> wrote: >> >>> How do you calculate MTBF? >> For a component? For an entire system? 217 or Bellcore/Telcordia or ... >> >> The Wikipedia article isn't a bad place to start. If you're tasked with >> doing a full-up parts-stress reliability prediction analysis, good luck! > > For a lithium ion battery charger. > > My brief post was a cry of despair. I ship these by the hundred. Now a > BIG US company wants them and I get asked for a bucket load of > information. ...as long as they PAY for the info and time to compile it. |