|There are two standards for platinum RTDs: The European standard and the American standard. The European standard, also known as the DIN or IEC standard, is considered the world-wide standard for platinum RTDs.
This standard, DIN/IEC 60751 (or simply IEC751), requires the RTD to have an electrical resistance of 100.00 Ω at 0°C and a temperature coefficient of resistance (TCR) of 0.00385 Ω/Ω/°C between 0 and 100°C.
There are three resistance tolerances for Thin Film RTDs specified in IEC60751:
Class AA (Formerly 1/3B) = ± (0.1+0.0017×t) °C or 100.00 ± 0.04Ω at 0°C
Class A = ± (0.15+0.002×t) °C or 100.00 ± 0.06Ω at 0°C41
Class B = ± (0.3+0.005×t) °C or 100.00 ± 0.12Ω at 0°C
Also, one special class not included in DIN/IEC60751:
Class 1/10B = ±1/10 (0.3+0.005×t) °C or 100.00 ± 0.012Ω at 0°C