soojuslikku stabiilsust loetakse saavutatuks siis, kui termiline toime 20 min jooksul muudab suhtmõõtehälvet vähem kui üks kümnendik vaadeldava suhtmõõtehälbe väärtusest tugitingimustel, thermal stability is considered to be reached when the change in percentage error as a consequence of thermal effects is during 20 min less than 1/10th of the limit of percentage error at reference conditions for the measurement under consideration