Most thermal analysis experiments are carried out under temperature ramp conditions where temperature is the independent parameter. Some experiments, however, are carried out under isothermal temperature conditions where the elapsed time to an event is measured as the independent parameter. Isothermal Kinetics (Test Methods E 2070), Thermal Stability (Test Method E 487), Oxidative Induction Time (OIT) (Test Methods D 3895, D 4565, D 5483, E 1858, and Specification D 3350 and Loss-on-Drying (Test Method E 1868) are common examples of these kinds of experiments.

Modern scientific instruments, including thermal analyzers, usually measure elapsed time with excellent precision and accuracy. In such cases, it may only be necessary to confirm the performance of the instrument by comparison to a suitable reference. Only rarely will it may be required to correct the calibration of an instrument'elapsed time signal through the use of a calibration factor.

It is necessary to obtain elapsed time signal conformity only to 0.1 times the repeatability relative standard deviation (standard deviation divided by the mean value) expressed as a percent for the test method in which the thermal analyzer is to be used. For those test methods listed in Section 2 this conformity is 0.1 %.