BS ISO 18927:2013 pdf download
BS ISO 18927:2013 pdf download.lmaging materials —Recordable compact discsystems- Method for estimating the life expectancy based on the effects of temperature and relative humidity.
4 Purpose and assumptions
4.1 Purpose
The purpose of this International Standard is to establish a methodology for estimating the life expectancy of information stored on recordable compact disc systems. This methodology provides a technically and statistically sound procedure for obtaining and evaluating accelerated test data.
The methodology deals only with the effects of temperature and humidity on the retrievability of stored information. For this reason, this International Standard is primarily directed to those storage applications, e.g. libraries and archives. in which exposure to other influences potentially detrimental to information life expectancy, such as chemical agents, intense light sources, and improper handling, is controlled and minimized.
4.2 Assumptions
The validity of the procedure defined by this International Standard relies on three assumptions:
— specimen life distribution is appropriately modelled by the lognormal distribution;
— the kinetics of the dominant failure mechanism is appropriately modelled by an F.yring acceleration model;
— the dominant failure mechanism acting at the usage condition is the same as that at the accelerated conditions.
Publications by Hamada and Stinson provide data indicating that these assumptions are applicable to compact dlsc•recordable (CD-R) systems (see reIerenceslSl andibl in the Bibliography).
5 MeasLirements
5.1 Summary
A sampling of 80 recorded discs shall be divided Into five groups according to a specified plan Each group of discs (test cell) shall be subjected to one of five test stresses, combinations of temperature and relative humidity. Periodically during the stress conditions, all discs from each stress group shall have their block error rate (BLER) measured. Data collected at each time interval for each Individual disc are then used to determine a lifetime for that disc.
The disc lifetimes at each stress level are fitted to a lognormal distribution to determine a mean lifetime forthe stress. The resulting five mean lifetimesare regressed against temperature and relative humidity according to an Eyring acceleration model. This model is then used to estimate the distribution of lifetimes at a usage condition.
5,2 Block error rate (BLER)
End-of-life is the occurrence of any loss of information. Ideally, each specimen is tested until the first loss of Information occurs. Realistically, this is ImpracticaL This International Standard considers max BLER to be a high-level estimate of the performance of the system. The objective of measuring BEER is to establish a practical estimation of the system’s ability to read recorded data without uncorrectable errors. A change in max BIER in response to the time at an accelerated temperature and humidity Is the principal quality parameter.
IEC 60908 states that the BIER averaged over any 10 s shall be less than 3 10-2. At the standard (IX) data rate, the total number of blocks per second entering the Cl-decoder is 7 350. Thus, an equivalent limit on BIER is 220 blocks per second.
A BIER of 220 is an arbitrary level chosen as a predictor of the onset of uncorrectable errors and thereby end-of-life A BIER of 220 corresponds to an upper limit for error correction As a result, lower BLER discs are recommended to use for long-term storage.
5.3 Test equipment
5.3.1 General requirements
A compact disc player that conforms to ISO/IIC 10149 and software capable ot producing a display or max BIER.
If it becomes necessary to replace the test equipment, the US National Bureau of Standards Handbook 91 shall be followed for correlating test equipment outputs.
The make, model, and version of the test equipment (including software) shall be reported with the test results.
5.3.2 Calibration and repeatability
Calibration according to the tester manufacturer’s procedure shall be performed prior to any measurement data being collected A calibration disc shall be available from an accredited source.
In addition to the calibration disc, one control disc shall be maintained at ambient conditions and its max BIER measured before and after each data collection interval. A control chart shall be maintained for this control disc.
The mean and standard deviation of the control disc shall be established by collecting at least five measurements. Should any individual max BIER reading differ from the mean by more than three times the standard deviation, the problem shall be corrected and all data collected since the last valid control point shall be re-measured.
5.4 Test specimen
5.4.1 General requirements
A test specimen is any disc that, after recording, meets ISO/IEC 10149 specifications and contains representative data extending to within 2 mm of the maximum recording diameter.
