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I am a computer Science student, and I have to write a program that models the expected reliability of a circuit given a circuit diagram. The issue is that I have no idea what that means, and my research has only come up with things that are very technical.

So can anyone give me a basic idea of what this means?

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    \$\begingroup\$ Is the question asking about microelectronic component lifetimes, valid digital logic output delay, or distribution grid scheduled maintenance? \$\endgroup\$ – tyblu Dec 3 '10 at 5:31
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    \$\begingroup\$ There's MTBF (useless for most things with software), the "bathtub failure curve", etc... \$\endgroup\$ – Nick T Dec 3 '10 at 5:35
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    \$\begingroup\$ It depends on how you classify failure. For example, say it's a power supply; would it have failed if the output got a bit noisier because the electrolytic capacitors had dropped in value slightly? Or would it have to be a catastrophic failure? \$\endgroup\$ – Thomas O Dec 3 '10 at 8:09
  • \$\begingroup\$ Could you post one of your circuit diagrams? That would also be helpful. A "circuit" is a very vague reference. \$\endgroup\$ – W5VO Dec 3 '10 at 8:09
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The simple way of thinking:

Each component has a failure rate. It can be measured in MTBF (mean time between failure) (as @Nick T said) or Failure Rate. Reliability is a number which states the probability that a component would still being working after an amount of time. In general for eletronic components it follows an exponential distribution. You can use it to calculate the probability of a component still being functional after a given time.

For a circuit with no security systems (back-ups, redundant circuitry, etc) the overall reliability is the product of each reliability.

If you have a backup circuit, for example two redundant capacitors on the power supply, the probability that the capacitor bank is still working is the sum of the two probabilities.

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