Siemens SIMATIC S7-1500 Manual page 16

Wiring
Block diagram and pin assignment for voltage measurement
The example in the figure below shows the pin assignment for a 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
16
CHx Channel or 8 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 8xU/I HS (6ES7531-7NF10-0AB0)
Manual, 12/2016, A5E03484886-AE