Measurement using a 4-wire connection system
Notes regarding the connection and operation of PT100 resistors:
This enables the module to supply X3 with a constant current via the CO1, CI1, CO2 and
CI2 terminals. The constant current is fed to the resistor to be measured where it is then
measured as the voltage drop. It is imperative to wire the connected constant current cables
directly to the resistor.
Measurements with 4-wire connections compensate for line resistances and return a
considerably higher degree of precision in comparison with 2-wire connections.
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Figure12-14 PT100 pin assignment
Measurement using a 3-wire connection system
The following pins must be jumpered at connector X3 in order to perform the measurement in
the PT100 using a 3-wire connection system:
• Temperature measurement with channel 1:
Short-circuit pin 2 (CI 1) and pin 4 (AI 1-) and connect the jumper at connector X3
• Temperature measurement with channel 2:
Short-circuit pin 6 (CI 2) and pin 8 (AI 2-) and connect the jumper at connector X3.
Note
Measuring accuracy
The accuracy of the temperature input becomes poorer: The resistance of the connecting
cable of the jumpered connecting cable falsies the measurement.
Connectable components
12.2PP 72/48D PN and PP 72/48D 2/2A PN
NCU 1750
134 Equipment Manual, 10/2023, A5E45627807B AH
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