ABB AC500 PLC Hardware Manual page 547

The internal power supply voltage for the module's circuitry is carried out via the I/O bus (pro-
vided by a bus module or a CPU). Thus, the current consumption from 24 VDC power supply at
the terminals L+/UP and M/ZP of the CPU/bus module increases by 2 mA per I/O module.
The external power supply connection is carried out via the UP (+24 VDC) and the ZP (0 VDC)
terminals.
The following figure shows the electrical connection of the I/O module.
2019/04/17
Because of their common reference potential, analog current inputs cannot be
circuited in series, neither within the module nor with channels of other mod-
ules.
For the open-circuit detection (cut wire), each analog input channel is pulled up
to "plus" by a high-resistance resistor. If nothing is connected, the maximum
voltage will be read in then.
NOTICE!
Risk of damaging the PLC modules!
Overvoltages and short circuits might damage the PLC modules.
– Make sure that all voltage sources (supply and process voltage) are
switched off before you begin with operations at the system.
– Never connect any voltages or signals to reserved terminals (marked with
---). Reserved terminals may carry internal voltages.
Generally, analog signals must be laid in shielded cables. The cable shields
must be earthed at both sides of the cables. In order to avoid unacceptable
potential differences between different parts of the installation, low resistance
equipotential bonding conductors must be laid.
Only for simple applications (low electromagnetic disturbances, no high require-
ment on precision), the shielding can also be omitted.
3ADR010121, 13, en_US
Device Specifications
I/O Modules > Analog I/O Modules
547