1
$\begingroup$

I have a list of components with their reliability, for example

Resistor [Fixed, Metal Film], Number used 168, Rating 50%, Failure rate 0.005, weighting factor 1.5.

I have calculated the total reliability for all of these components, for the example I think it is 1.26. The next step is M.T.B.F, reliability over 5 days and over 28 days of 8 hour use.

I am currently a little confused as to what I should be doing with these figures I have worked out, do I add them? Multiply them? and then what?

Please help.

2 Answers 2

1

Hint for MTBF: The minimum of exponential random variables with rates $\lambda_1,\ldots,\lambda_n$ is an exponential random variable with rate $\lambda_1 + \cdots + \lambda_n$ (see Wikipedia).

As for reliability, I can't help since I've never heard of this parameter.

0

The reliability seems to be a failure rate, maybe FIT=failures per billion hours (don't ask me where the acronym comes from). This usually assumes an exponential distribution of failures. Then MTBF is mean time between failures, which would be just the inverse of the failure rate if the unit were active all the time. In our business (and I don't know how standard this is) if the unit is powered off the failure rate is 1/10 of the powered on rate. If that is your model, the chance of non-failure over 5 days the chance of non-failure in 40 powered hours times the chance of non-failure in 80 non-powered hours. Given your failure rate, can you calculate the chance of failure in 40 hours?