SCC-RTD01 Resistance Temperature Detector User Guide
8
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For temperatures above 0
°
C, the C coefficient equals 0. Therefore, for
temperatures above 0
°
C, this equation reduces to a quadratic. If you
pass a known current,
I
EX
, through the RTD and measure the voltage
developed across the RTD,
V
0
,
you can use the following formula to
solve for
t
:
where
V
0
is the measured RTD voltage.
I
EX
is the excitation current.
Most platinum RTD curves conform to one of the following three
standardized curves:
•
DIN 43760 standard
•
U.S. Industrial or American standard
•
International Temperature Scale (ITS)–90 (for use with
wire-wound RTDs)
Table 1.
Callendar-Van Dusen Coefficients for Platinum RTDs
Standard
Temperature
Coefficient
A
B
C
DIN 43760
0.003850
3.9080
×
10
–3
–5.8019
×
10
–7
–4.2735
×
10
–12
American
0.003911
3.9692
×
10
–3
–5.8495
×
10
–7
–4.3235
×
10
–12
ITS-90
0.003926
3.9848
×
10
–3
–5.870
×
10
–7
–4.0000
×
10
–12
t
2
V
0
I
EX
R
0
–
(
)
I
EX
R
0
A
A
2
4
B V
0
I
EX
R
0
–
(
)
(
)
I
EX
R
0
(
)
⁄
+
+
[
]
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=
