Description of I/O extension modules
105542_en_05 PHOENIX CONTACT 93 / 198
4-wire connection technology
The RAD-PT100-4-IFS does not support 4-wire connection technology.
• If you want to use a 4-wire sensor, only connect three of the four cables.
• The fourth cable should be left unwired. Otherwise there will be a different resistance in
the +I and -I cables owing to the parallel connection of two cable resistances.
Figure 7-7 4-wire connection technology
7.2.2 Measuring errors when using 2-wire connection
technology
Figure 7-8 Systematic temperature measuring error ΔT depending on cable length l
Curves depending on cable cross section A
A = 0.25 mm
2
A = 0.5 mm
2
A = 1.0 mm
2
A = 1.5 mm
2
(Measuring error valid for: copper cable χ = 57 m/Ωmm
2
, T
A
= 25°C, and Pt100 sensor)
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+
(U+)
RTD
ϑ
RL
I–
U–
0 2,5 5 7,5 10 12,5 15 17,5 20
0
2
4
6
8
T [K]
I [m]
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