F-8 Temperature Equations Model 2750 Multimeter/Switch System User’s Manual
RTD equation
The temperature vs. resistance readings listed in the RTD reference tables are calculated
using the Callendar-Van Dusen equation:
R
RTD
= R
0
[1 + AT + BT
2
+ CT
3
(T-100)]
where; R
RTD
is the calculated resistance of the RTD
R
0
is the known RTD resistance at 0°C
T is the temperature in °C
A = alpha [1 + (delta/100)]
B = -1 (alpha)(delta)(1e-4)
C = -1 (alpha)(beta)(1e-8)
The alpha, beta, and delta values are listed in Table F-10.
Example — Calculate the resistance of a PT100 RTD at 100°C (T). The following R
0
(Ω
at 0°C), alpha, beta, and delta values are used for the PT100 RTD (see Table F-10):
T = 100°C
R
0
(Ω at 0°C) = 100Ω
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
Table F-10
RTD parameters
Type Standard Alpha Beta Delta Ω at 0°C
PT100 ITS-90 0.00385055 0.10863 1.49990 100Ω
D100 ITS-90 0.003920 0.10630 1.49710 100Ω
F100 ITS-90 0.003900 0.11000 1.49589 100Ω
PT385 IPTS-68 0.003850 0.11100 1.50700 100Ω
PT3916 IPTS-68 0.003916 0.11600 1.50594 100Ω
2750-900-01.book Page 8 Wednesday, August 3, 2011 7:56 AM
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