scope:

This standard specifies the requirements and temperature/resistance relationship for industrial platinum resistance temperature sensors later referred to as "platinum resistors" or "resistors" and industrial platinum resistance thermometers later referred to as "thermometers" whose electrical resistance is a defined function of temperature.
The International Standard applies to platinum resistors whose temperature coefficient á, defined as
á = R 100 - R 0
R0 . 100 C
is conventionally written as á = 3.851 x 10-3 °C-1, where R100 is the resistance at t = 100 °C and R0 is the resistance at t = 0 °C.
Values of temperature in this standard are in terms of the International Temperature Scale of 1990, ITS-90. Temperatures in degrees Celsius are denoted by the symbol t, except in Table 1 where the full nomenclature t90/°C is used.
The standard covers resistors or thermometers for all or part of the temperature range -200 °C to +850 °C with different tolerance classes, which may cover restricted temperature ranges.
For temperature/resistance relationships with uncertainties <0,1 °C, which are possible only for resistors or thermometers with exceptionally high stability and individual calibration, a more complex interpolation equation than is presented in this standard may be necessary.
The specification of such equations is outside the scope of this standard.