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 α, defined as 0 100 C 100 0 ⋅ ° − = R R R α is conventionally written as α = 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.