Failure Rate Calculations Using a Programmable Calculator

This paper describes a TI 59 program which calculates the acceleration factor between any two temperatures, equivalent unit-hours at one temperature based on actual test hours at a second temperature, the x2 approximation at any of seven s-confidence levels, and the s-confidence limit failure rate estimate in both %/1000 hours and FITs. The program allows numerous entries of separate sample results which the calculator stores and then performs a single failure rate estimate calculation. Required inputs are test temperature, temperature at which the failure rate estimate is desired, the activation energy, and the number of failures during the test. The equations for the program are reviewed and tables are included showing all labels and memories used, and the 355 program steps listing.