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ISO 18926-2012 pdf free download
ISO 18926-2012 pdf free download.Imaging materials — Information stored on magneto-optical (MO) discs — Method for estimating the life expectancy based on the effects of temperature and relative humidity
Matérlaux pour Pimage — In formation stockée sur disques optomagnétiques (MO) — Méthode destimation de l’espérance de vie basée sur les effets de ía tern pérature et de l’humiditë relative.
In order to estimate the log mean and log standard deviation of a lognormal distribution, (see Aitchison and Brown in Clause 3) at least ten failures shall be observed, Observing at least ten failures may not be a problem for a realistic test time at 80 °C185 % RH but becomes more difficult at milder stress temperature and relative humidity combinations. Assigning a larger percentage of the specimens to the milder stresses increases the chance of observing the necessary number of failures within a practical time interval.
Specimens that have riot failed at the end of the test duration shall be time censored. This is also known as Type I censoring (see Reference [2), page 233).
If ten failures are not observed by the end of the test duration, then failures may be estimated. To compute the estimated failure time for each disc, it is necessary to first determine a transformation of the BER, such as ln(BER), that results in a linear time dependence. Standard linear regression techniques shall be used to find the best fit to the transformed data. The failure time for each disc shall then be computed by interpolation or extrapolation using each disc’s regression equation.
6.4 lime intervals
For a test plan where the exact time-to-failure” is to be the result of extrapolated rate data, no fewer than five time intervals for data collection are required. The baseline measurement (at s = 0) is one of these data points. Within a stress condition, the intervals shall be constant.
As the stress conditions get milder, the intervals become longer. Longer time intervals provide the opportunity for more failures to occur at the milder stress conditions.
6.4.2 Test plan
Table 1 specifies the temperatures, relative humidities, time intervals, minimum total time and specimen distributions for each stress condition. A separate group of specimens is used for each stress condition. This constitutes a constant Stress” test plan.
All temperatures have a permitted range of ± 2 °C; all relative humidities have a permitted range of ± 3 % RH.
The stress conditions tabulated in Table 1 offer sufficient combinations of temperature and relative humidity to satisfy the mathematical requirements of the Eyring model (see 7.2), to demonstrate linearity of BER versus time, and to produce a satisfactory confidence level to make meaningful conclusions.
6.4.3 Measurement conditions
Discs shall be equilibrated to the environment in which they will be tested. Foreign surface contaminants shall be cleaned from the disc prior to testing.ISO 18926-2012 pdf free download.
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