Chapter 4
Theory of Operation
©
National Instruments Corporation
4-7
defined as the change in RTD resistance from 0 to 100
°
C, divided by the
resistance at 0
°
C, divided by 100
°
C:
where
R
100
is the resistance of the RTD at 100
°
C.
R
0
is the resistance of the RTD at 0
°
C.
For example, a 100
Ω
platinum RTD with
α
= 0.003911 has a resistance of
139.11
Ω
at 100
°
C.
Figure 4-3 displays a typical resistance-temperature curve for a 100
Ω
platinum RTD.
Figure 4-3.
Resistance-Temperature Curve for a 100
Ω
Platinum RTD,
α
= 0.00385
α
(
Ω
/
Ω
/
°
C
)
R
100
R
0
–
R
0
100
°
C
×
-----------------------------
=
480
400
320
240
160
80
320 400 480 560 640 720 800 880
0
80 160 240
960
