National Instruments Module SCXI-1503 - Manual (Page 39)

Chapter 4 Theory of Operation
© National Instruments Corporation 4-9 SCXI-1503 User Manual
For temperatures above 0
°C, coefficient C equals 0, reducing this equation
to a quadratic. If you pass a known current, I
EX
, through the RTD and
measure the output voltage developed across the RTD, V
0
, you can solve
for T as follows:
where
V
0
is the measured RTD voltage.
I
EX
is the excitation current.
US Industrial
Standard
American 3911 100
Ω
A = 3.9692
× 10 –3
B = –5.8495
× 10 –7
C = –4.233
× 10 –12
ITS-90 3928 100
Ω
A = 3.9888
× 10 –3
B = –5.915
× 10 –7
C = –3.85
× 10 –12
1 No standard. Check TCR.
Table 4-1. Platinum RTD Types (Continued)
Standard
Temperature
Coefficient of
Resistance
(TCR, PPM)
Typical
R
0
Callendar-Van
Dusen Coefficient
T
R
0
V
0
I
EX
------- –
–0.5 R
0
A R
0
2
A
2
4R
0
B R
0
V
0
I
EX
------- – ⎝ ⎠
⎛ ⎞
– +
⎝ ⎠
⎜ ⎟
⎛ ⎞
------------------------------------------------------------------------------------------------ =