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Entry type: FAQ Entry ID: 40913432, Entry date: 06/24/2020
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How do you connect a sensor to the analog signal modules of the S7-1200/S7-1500 and the ET 200MP?

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The following entry also shows you how to connect a sensor with 3-wire connection (3-wire measuring transducer) to the analog signal modules of the SIMATIC.

Non-isolated voltage sensor with ground connection (3-wire connection)
The manuals of the modules (for example ET 200M, ET 200SP, ...) only describe the 2-wire and 4-wire connections (2-wire and 4-wire transducers). You also have the option of connecting sensors with 3-wire connection (3-wire transducers) to the SIMATIC analog signal modules.

Example for the SIMATIC ET 200SP analog input module AI 4xI 2-/4-wire ST

For this you have to observe the following:

  • The analog module must be configured as a 4-wire measuring transducer.
  • Current input negative, channel n must be bridged to ground.

Fig. 1 shows the connection to an S7-1200 AI input:
 


Fig. 1


Potential-free voltage sensor (4-wire connection)
A field sensor with the following properties can be connected to the analog input signal modules of S7-1200:

  • Transducer with voltage output: +/-10 V, +/-5 V or +/-2.5 V or
  • 2-wire measuring transducer: 4-20 mA

You can select the type of measurement (voltage or current) via 2 channels in each case. The following figures show examples of how to connect different sensor types (voltage power supply: 24 V DC) to the analog signal module SM 1231 AI 4 x 13 Bit (channel 0):
 


Fig. 2


Current measurement via a 2-wire measuring transducer
Fig. 3 shows a 2-wire transducer for 4-20mA.
 


Fig. 3


Further Information
More information is available in the TIA Portal Information System under:

Additional Keywords
2-wire, 3-wire, 4-wire

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