ABB · AC500-S Safety Controller
The measured process voltage at the I/O module has exceeded the permissible upper limit. This can indicate an overvoltage condition in the field wiring or power supply, potentially damaging connected sensors or actuators and leading to unsafe operating conditions.
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Using a calibrated multimeter, measure the voltage at the affected I/O module input terminals (e.g., AI1+ to AI1-) to verify it exceeds the module's specified maximum input voltage.
Isolate the connected sensor/actuator and measure its output voltage independently to confirm it is operating within its specified range.
Trace the external power supply connected to the I/O module's process voltage input and verify its output voltage (e.g., at the output terminals of a 24VDC PSU) is correct and stable.
Inspect the wiring for the specific channel for any signs of short circuits to higher voltage lines or incorrect terminal connections.
Verify the I/O module's configuration in the engineering software (e.g., Parameter P3-01 for input range) matches the type and voltage range of the connected sensor (e.g., 0-10V, 0-20mA, 0-50V).