Did you send your RTD for calibration? Did you get Certificate of Calibration? and now you have realized your unit ask for coefficients? So are you in doubt what to do? Are you calling your laboratory, but they do not want to deal with you? Or just they do not want to share with you how to get coefficients for your unit? See the procedure below:
Let’s see. On our certificate are given following datas:
Actual Indicated
T R
Temp. Resistance
(°C) (Ω)
25.00 110.336
36.99 115.068
50.00 120.201
89.99 136.851
124.99 149.37
we are going to use these values to write a set of equations to find out coefficients A, B, C of the polynomial function
T = A + B·R + C·R2
——————————————————————————–
Set of Equations
T1 = A + B·R1 + C·R12
T2 = A + B·R2 + C·R22
T3 = A + B·R3 + C·R32
T4 = A + B·R4 + C·R42
T5 = A + B·R5 + C·R52
Solution: – use matrix formula
(type in Matlab)
M1 = [T1;T2;T3;T4;T5]
M2=[1 R1 R1^2;1 R2 R2^;1 R3 R3^2;1 R3 R3^2;1 R4 R4^2;1 R5 R5^2]
Solution
S= inv(M2’*M2)*M2’*M1
Coefficients are:
S=(32.221 2.300 0.001)
If you want to know more about it, just give me a call 😉