Description of I/O extension modules
3827_en_B
PHOENIX CONTACT
Figure 3-5
2-wire connection technology
3-wire connection technology
With 3-wire connection technology, the temperature-related voltage is measured several
times. Corresponding calculations additionally reduce the effect of the cable resistance on
the measurement result. The results are almost as good as those achieved using the 4-wire
technology.
The cable resistances R
L
at the terI and -I must have the same value. This allows
you to subtract the established cable resistance from the measurement result and to get the
Pt 100 platinum resistance value.
Figure 3-6
3-wire connection technology
µC
2.1
2.2
2.3
3.1
3.2
3.3
5.1
5.2
5.3
4.1
4.2
4.3
IO-MAP
0 1
DC
DC
IFS
IFS
A
D
1mA
A
D
1mA
A
D
1mA
A
D
1mA
-I2
-U2
+I2
+I1
-U1
-I1
+I3
-U3
-I3
+I4
-U4
-I4
RL
RL
I+
I–
RTD
ϑ
µC
2.1
2.2
2.3
3.1
3.2
3.3
5.1
5.2
5.3
4.1
4.2
4.3
IO-MAP
0 1
DC
DC
IFS
IFS
A
D
1mA
A
D
1mA
A
D
1mA
A
D
1mA
-I2
-U2
+I2
+I1
-U1
-I1
+I3
-U3
-I3
+I4
-U4
-I4
RL
I+
RTD
ϑ
RL
I–
U–