Process voltage too low

What does 11 mean?

The measured process voltage at the I/O module has fallen below the permissible lower limit. This suggests an undervoltage condition, which can cause connected sensors or actuators to operate unreliably or fail, compromising system safety.

• Undervoltage condition from the external process power supply connected to the I/O module's input terminals (e.g., terminal X1.1, X1.2), potentially due to an overloaded PSU.
• Partial or complete break in the signal cable or a loose connection to the sensor or at the I/O module terminals (e.g., AI1+, AI1-).
• Malfunction of the connected sensor, causing it to output a voltage or current below its specified minimum operating range.
• High resistance in the signal path due to corroded terminals, resulting in a significant voltage drop before reaching the module.
• Internal component failure within the I/O module causing a misinterpretation of the input voltage or a fault in its measurement circuitry.

Click steps to track your progress.

1. 1

   Using a calibrated multimeter, measure the voltage at the affected I/O module input terminals (e.g., AI1+ to AI1-) to verify it is below the module's specified minimum input voltage.

2. 2

   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 within specified limits.

3. 3

   Perform a continuity test on the signal cable for the affected channel from the sensor output to the I/O module terminals to identify any breaks or high resistance.

4. 4

   With the sensor isolated, measure its output voltage or current directly to confirm it is supplying the expected signal level.

5. 5

   Inspect all screw terminals or spring clamps for the affected channel at both the sensor and the I/O module for tightness and signs of corrosion.