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E-4
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 E-2
RTD parameters
Type
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
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
C = -1 (0.00385)(0.10863) (1e-8)
= -1 (0.000418)(1e-8)
= - 4.18e-12
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)
Standard
ITS-90
ITS-90
ITS-90
IPTS-68
IPTS-68
Model 2790 SourceMeter
3
(T-100)]
Table
E-2.
Alpha
Beta
0.003850
0.10863
0.003920
0.10630
0.003900
0.11000
0.003850
0.11100
0.003916
0.11600
®
Switch System Reference Manual
Ω at 0°C
Delta
1.49990
100Ω
1.49710
100Ω
1.49589
100Ω
1.50700
100Ω
1.50594
100Ω
(Table
E-2):
(Ω
0
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