SNOAA67A May 2021 – June 2022 TMP116 , TMP117 , TMP1826 , TMP61 , TMP63 , TMP64

A resistance temperature detector is a passive circuit element whose resistance increases as temperature increases. They are generally constructed using platinum, copper, or nickel, and one major advantage of RTDs is that they support a wide span of temperature, ranging from –200°C to +850°C. The accuracy limits of an RTD are defined by the class, or grade, of the RTD. The characteristics of platinum, copper, or nickel determine the linear approximation of resistance versus temperature within the 0°C to 100°C temperature range. The platinum RTD is known for its strong linearity and repeatability characteristic.

DIN/IEC 60751 is considered the worldwide standard for platinum RTDs. For a PT100 RTD, the standard requires the sensing element 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°C and 100°C.

Equation 1 and Equation 2 define the resistance-to-temperature relation for temperature ranges above and below 0°C.

Equation 1.
${R}_{T}={R}_{0}\left[\left(1+\mathrm{A}\mathrm{T}\right)+{\mathrm{B}\mathrm{T}}^{2}\right]\mathrm{}\mathrm{f}\mathrm{o}\mathrm{r}\mathrm{}\mathrm{T}\mathrm{}\ge 0\mathrm{\mathbb{C}}$

Equation 2.
${R}_{T}={R}_{0}\left[\left(1+\mathrm{A}\mathrm{T}\right)+{\mathrm{B}\mathrm{T}}^{2}+{\mathrm{C}\mathrm{T}}^{3}(100-T)\right]\mathrm{}\mathrm{f}\mathrm{o}\mathrm{r}\mathrm{}\mathrm{T}0\mathrm{\mathbb{C}}\mathrm{}$

with:

- A = 3.9083 × 10
^{–3} - B = –5.775 × 10
^{–7} - C = –4.183 × 10
^{–12}