Siemens SIMATIC S7-1500 Manual page 16

Wiring
3.1 Wiring and block diagrams
Connection: Voltage measurement
The example in the following figure shows the pin assignment for voltage measurement.
①
Analog-to-digital converter (ADC)
②
Backplane bus interface
③
Supply voltage via power supply element
④
Equipotential bonding cable (optional)
Figure 3-2 Block diagram and pin assignment for voltage measurement
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CHx Channel or 4 x channel status (green/red)
RUN Status display LED (green)
ERROR Error display LED (red)
PWR LED for power supply (green)
Analog Input Module AI 4xU/I/RTD/TC ST (6ES7531-7QD00-0AB0)
Manual, 09/2016, A5E32366209-AC