How do you connect a sensor to the analog signal modules of the S7-1200/S7-1500 and the ET 200MP?
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:
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):
Current measurement via a 2-wire measuring transducer
Fig. 3 shows a 2-wire transducer for 4-20mA.
More information is available in the TIA Portal Information System under:
- Technical data of the analog input modules
- For an S7-1200/S7-1500 controller in STEP 7 (TIA Portal), how do you scale integer values in real numbers and vice versa for analog inputs and outputs?
2-wire, 3-wire, 4-wire
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