At 0º C, A Platinum RTD has a resistance of 100 O & a temperature co-efficient of about 0.00385 O/ O / ºC. These non-linearties are described in Callender-Van Duesen equation.
This equation consists of both a linear portion & a non- linear portion.
Range 200 to 0ºC: R (t) [Ω] = R (1 + At + Bt2 + C (t - 100ºC) t3)
Range 0 to 850ºC: R? (t) [O] = R (1 + At + Bt?)
With: R0 is resistance at 0 ºC
A = 3, 9083 x 10ˉ³ °Cˉ¹
B = -5,775 x 10ˉ⁷ °Cˉ²
C = -4,183 x 10ˉ¹² °Cˉ⁴