How to assess Reliability of an electronic unit - calculation of MTBF(Mean Time Between Failure)

This article emphasizes on assessment of reliability of charge sensitive amplifier. Part stress method is used for assessment of the Reliability.  Failure rate data for various components in the amplifier was calculated using MIL-HDBK-217.MTBF is determined for the unit. 


Reliability

Reliability is the probability that the part will operate without failure for the time period ‘t’ under given operating conditions.

R(t) = e-λt ;

‘λ’ is failure rate of item and is a constant for any given stress, temperature and quality conditions.

The unit failure rate is given by sum of individual failure rates of ‘n’ independent components.


Mean Time between failure (MTBF)

MTBF is mean or average time before failure of the unit during useful life period. It is expressed as 1/λ

The circuitry of amplifier is shown in following figure







Failure Rate of the Amplifier

 The total failure rate of the amplifier is derived by addition of failure rates of all the components.

The total failure rate of the amplifier is calculated and found to be ~ 3.4447 x 10-6 failures/hr.

The MTBF of the amplifier is  2.9 x 10⁵ hrs


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