According to IEC60335-2-11:1993 fig 101 and IEC60335-2-6:1997 fig 104, such as requirements preconditioning of household and similar electrical appliances drum dryers and in vertical ranges, hobs, ovens and other were surface temperature rise measurement.

Standard:
IEC 60335-2-11 “Household and similar electrical appliances – Safety – Part 2-11: Particular requirements for tumble dryers” fig 101
IEC 60335-2-6 “Household and similar electrical appliances – Safety – Part 2-6: Particular requirements for stationary cooking ranges, hobs, ovens and similar appliances” fig 104
IEC 60584-1 “Thermocouples – Part 1: EMF specifications and tolerances”