MES Counters can be set to capture the value of a hardware PLC counter, at any desired store rate, as Tag Collector History entries. These stored counter value records can be inserted, deleted or edited using the MES Value Editor, or added via scripting with system.mes.addTagCollectorValue or system.mes.addTagCollectorValues. This provides the ability to repair missing or excessive counts by the hardware PLC long after the production run has completed. The new entry is designed to mimic what the counter value should have been at the timestamp provided (can be higher or lower than the previous entry), resulting in more accurate counts and OEE calculations.
If a new Tag Collector History entry is made for an MES Counter, the MES software will calculate the difference in count value between the new entry and entry previous to it. It will then add this difference to all of the existing entries forward in time to the present. However, the hardware PLC counter value will no longer reflect the adjusted production count and will need to be written with a matching adjusted value.
Applies To and Version Info
If a new historical entry is made to the Tag Collector History for an MES Counter, the count delta will be automatically propagated forward to the present by the MES software, as shown in the example below:
- The hardware PLC counter on the production line is reflecting a 2 units/minute production rate from 9:00 AM through 10:10 AM.
- The MES Counter based on this PLC counter stores a Tag Collector entry every 10 minutes (PLC counter reads 20 counts higher each time).
- At 1:00 PM (long after the production run), it is discovered that 17 additional parts were produced by 9:15 AM that were missed by the hardware PLC counter, so the operator adds it manually after the existing 9:10 AM entry, using the MES Value Editor.
- The Sepasoft software automatically adjusts all of the Tag Collector entries for the MES Counter from the entry point through to the present (each count is increased by 17).
|Time||Hardware PLC counter value||Original Tag Collector history|
(store rate = 10 mins)
|New Tag Collector entry made for MES Counter value |
(edit made at 1:00 PM)
|Updated Tag Collector history|
(after S/W propagates the delta in value forward in time to the present)
|9:15 AM||137 (+17 counts)||137*|
* Tag Collector entry manually entered by the operator ~1:00 PM
** updated values (count values adjusted by the MES software immediately after the operator makes the new historical entry with a 9:15 AM time stamp)
PLC does not match Tag Collector value
Note that the hardware PLC counter is at 240 at 10:10AM because it missed the 17 parts during the production run, but after the operator manually adds the parts in historically at 9:15 AM, the recorded Tag Collector value for 10:10AM is now 257 and does not match the PLC count value.
How this affects production lots
If the new Tag Collector entry is made for a previous lot that has completed, but another lot is now being run on the same line (same MES Counter being utilized), then the counts for the new lot currently running on the line will have its Tag Collector entries also augmented by the same delta in count value. Therefore, there will be no net change in the recorded counts for the new lot that is currently running, since all recorded count values were augmented by the same amount.
It is recommended that after making a manual entry in the Tag Collector History to adjust the historical MES Counter values recorded, that the hardware PLC be immediately adjusted by the same amount, so the recorded values match the PLC counter again. In the example above, after making the manual entry at the 9:15 AM spot in the timeline, the operator should immediately adjust the hardware PLC counter value by +17 counts so it keeps pace with the recorded values.
Be mindful of how manual adjustments affect production data
- When making manual entries in the Tag Collector History for MES Counters, be mindful of how the new counter values might affect OEE or tracking data, especially if the entry is made while the production line is still running, or if reports have already been generated that do not include the count adjustment.
- When updating the PLC counter to match the Tag Collector history, be mindful to avoid a time slot where the PLC counter might increment between the time that the counter is read and when the repaired value is written back out (it will miss the increment).
MES Counter, MES Value Editor, system.mes.addTagCollectorValue, system.mes.addTagCollectorValues