Applicable Systems
GOT2000 Series
Symptoms
Alarm history shows duplicate entries with identical timestamps every second.
Possible Causes
- Alarm trigger bit in the PLC ladder logic chattering due to marginal sensor threshold.
- GOT alarm collection cycle set too fast (e.g., 100 ms) for the process dynamics.
- Alarm display filter 'Combine same alarms' disabled in the project settings.
Troubleshooting Steps
- Step 1: Monitor the PLC trigger bit with GX Works3 and add a one-shot or hysteresis.
Bit transitions only once per true alarm event. - Step 2: Increase the GOT alarm sampling interval to 1 second or match the PLC scan.
Duplicate entries cease and each alarm appears only once per occurrence. - Step 3: Enable the 'Combine same alarms' option in GT Designer3 alarm display settings.
Consecutive identical alarms are grouped into a single line with a count badge.
How to Reset
Add hysteresis to the PLC alarm trigger, slow the GOT sampling rate, and enable alarm combining.
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Source: Mitsubishi GT Designer3 Alarm Function Manual
Category: HMI
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