RTD(t) = R0 [1 + A*t + B*t*t + C (t 100°C)t*t*t ] t<= 0

RTD(t) = R0 [1 + A*t + B*t*t ] t>= 0

I have to calculate T from known value of R. For that I have to find inverse transfer function.

Roots of second equation are easy to find as it is quadratic.

But can we find roots of first equation also as it is of fourth order.

However for project, I have used best fit polynomial method & can calculate value of T from known R.

This is just for knowledge that if exact inverse transfer can be calculated for 4th order polynomial.