11-17
ET 200L, ET 200L-SC and ET 200L-SC IM-SC Distributed I/O Device
EWA 4NEB 780 6009-02c
11.9
Connecting resistance thermometers and resistors
The resistance thermometers and resistors are measured by means of a 4-con-
ductor system. A constant current is fed via terminals IC + and IC – to the
resistance thermometers and resistors. The resulting voltage at the resistance
thermometer and resistor is measured via terminals M
+
and M
–. Very pre-
cise measurement results are thus obtained at the 4-conductor connection.
Figure 11-7 shows how to implement the 4-conductor connection for resist-
ance thermometers/resistors.
Slot A
AI RTD
Slot C
Slot B
C1
C2
C3
C4
B1
B2
B3
B4
A1
A2
A3
A4
1L+
2L+
1M
2M
+24V
M
M+
IC+
M–
IC–
Figure 11-7 4-Conductor Connection for Resistance Thermometers and Resistors
(Example TB 16SC)
4-Conductor
Connection
SC Analog Electronic Modules – Parameters