Rtd Equation - Keithley 2750 User Manual

F-8 Temperature Equations

RTD equation

The temperature vs. resistance readings listed in the RTD reference tables are calculated
using the Callendar-Van Dusen equation:
R
RTD
where; R
The alpha, beta, and delta values are listed in
Table F-10
RTD parameters
PT100
D100
F100
PT385
PT3916
Example — Calculate the resistance of a PT100 RTD at 100°C (T). The following R
at 0°C), alpha, beta, and delta values are used for the PT100 RTD (see
T = 100°C
R (Ω at 0°C) = 100Ω
0
alpha = 0.003850
beta = 0.10863
delta = 1.49990
Using the above alpha, beta, and delta values, A, B, and C are calculated as follows:
A = 0.00385 [1 + (1.4999/100)]
= 0.00385 (1.014999)
= 0.00391
B = -1 (0.00385)(1.4999)(1e-4)
= -1 (0.00577)(1e-4)
= -5.77e-7
2
= R [1 + AT + BT + CT
0
is the calculated resistance of the RTD
RTD
R is the known RTD resistance at 0°C
0
T is the temperature in °C
A = alpha [1 + (delta/100)]
B = -1 (alpha)(delta)(1e-4)
C = -1 (alpha)(beta)(1e-8)
Type Standard
ITS-90
ITS-90
ITS-90
IPTS-68
IPTS-68
Model 2750 Multimeter/Switch System User's Manual
3
(T-100)]
Table F-10.
Alpha Beta
0.00385055 0.10863
0.003920 0.10630
0.003900 0.11000
0.003850 0.11100
0.003916 0.11600
Ω at 0°C
Delta
1.49990 100Ω
1.49710 100Ω
1.49589 100Ω
1.50700 100Ω
1.50594 100Ω
0
Table F-10):
(Ω