ANSI IT9.27-1999 pdf download Life Expectancy of Information Stored in Recordable Compact Disc Systems – Method for Estimating, Based on Effects of Temperature and Relative Humidity
4Measurements
4.1 Summary A sampling of eighty recorded discs is divided into five groups according to a specified plan. Eachgroup of discs is exposed to one of five stresses, combinations of temperature and relativehumidity. Periodically during the course of the xposure, all discs from each stress group havetheir block error rate measured. Data collected at each test interval for each individual disc areused to determine a lifetime for that disc. The disc lifetimes at each stress are fitted to a loanormal distribution to determine a mean lifetimefor the stress. The resulting five mean lifetimes are regressed against temperature and relativehumidity according to an Eyring acceleration model. This model is then used to estimate thedistribution of lifetimes at a usage condition.
4.2 BLER End-of-life is the occurrence of any loss of information. ldeally, each sample is tested until thefirst loss of information occurs. Realistically, this is impractical. This standard considersmaximum BLER to be a high-level estimate of the pertormance of the system.
The objective ofmeasuring BLER is to establish a practical estimation of the system’s ability to read the recordeddata without uncorrectable error. Change in maximum BLER in response to the time ataccelerated temperature and humidity is the principal quality parameter. ISO/IEC 908 states that the BLER averaged over any 10 seconds shall be less than3x10,At the standard (1X) data rate, the total number of blocks per second entering the C1.decoder is 7350. Thus, an equivalent limit on BLER is 220 blocks/second. For the purposes of this standard, recorded data is considered to have reached end-of-life whenthe BLER, measured as erroneous blocks per second, exceeds 220 anywhere on the disc, i.e.when max BLER exceeds 220. lt is recognized that the correlation between actual loss ofinformation and max BLER is very system dependent.A BLER of 220 is an arbitrary level chosenas a predictor of the onset of uncorrectable errors and thereby end-of-life.
4.3 Test equipment Any compact disc test system (tester) that conforms to ISO/EC 10149 may be used.The make, model, and version of the test equipment (including software) shall be reported withthe test results.
4.3.1 Calibration and repeatability A calibration according to the tester manufacturer’s procedure shall be performed prior to anymeasurement data being collected. A calibration disc shall be available from the testermanufacturer. n addition to the calibration disc one control disc shall be maintained at ambient conditions, andits max BLER measured before and after each data collection interval.A control chart shall bemaintained for this control disc.
The mean and standard deviation of the control disc shall be established by collecting at least fivemeasurements. Should any individual max BLER reading differ from the mean by more thanthree times the standard deviation, the problem shall be corrected and all data collected since theast valid control point shall be remeasured lf it becomes necessary to replace the tester, the National Bureau of Standards Handbook 91 [3)shall be followed for correlating tester outputs.