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MTBF can be calculated as the arithmetic mean (average) time between failures of a system. The term is used for repairable systems while mean time to failure (MTTF) denotes the expected time to failure for a non-repairable system. [1] The definition of MTBF depends on the definition of what is considered a failure.
For example, AFR is used to characterize the reliability of hard disk drives.. The relationship between AFR and MTBF (in hours) is: [1] = (/) This equation assumes that the device or component is powered on for the full 8766 hours of a year, and gives the estimated fraction of an original sample of devices or components that will fail in one year, or, equivalently, 1 − AFR is the fraction of ...
However, using a fixed failure rate to calculate MTBF is only valid if the failure rate is constant over time, such as within the flat region of the bathtub curve. In many cases where MTBF is quoted, it refers only to this region; this type of MTBF cannot be used to give an accurate calculation of the average lifetime of a system, as it ignores ...
Software reliability is the probability that software will work properly in a specified environment and for a given amount of time. Using the following formula, the probability of failure is calculated by testing a sample of all available input states. Mean Time Between Failure(MTBF)=Mean Time To Failure(MTTF)+ Mean Time To Repair(MTTR)
where MTBF is the nonredundant mean time between failures and FFAS is the fraction of failures for which the failed equipment is automatically bypassed. References
A worst-case circuit analysis should be performed on all circuitry that is safety and financially critical. Worst-case circuit analysis is an analysis technique which, by accounting for component variability, determines the circuit performance under a worst-case scenario (under extreme environmental or operating conditions).
Mean Time Between Failure (MTBF) depends upon the maintenance philosophy. If a system is designed with both redundancy and automatic fault bypass, then MTBF is the anticipated lifespan of the system if these features cover all possible failure modes (infinity for all practical purposes). Such systems will continue without noticeable ...
MTBF is usually given in years of device operation; to put it into perspective, one FIT equals to approximately 1,000,000,000 / (24 × 365.25) = 114,077 times longer between errors than one-year MTBF.