Edge historian not syncing latest value to main database

Ignition
1

I have an edge device with historian enabled. It was syncing to Database A, and I recently moved it over to Database B.

Everything seems to be ok except that it does not show the very last value on the trends. For example, if a value went from 10 to 15, it would show 10 in the easy chart. When the value goes from 15 to 20, then the easy chart would show 15. So its not updating the current value.

Also, since the database switch, the historical tags do not show up in the tag browse tree until a value has changed. So, if Tag A is a boolean with a value of False, it will not show up until it turns True. Is there any way to force these starting values into the new database?

I do have the tag browse tree pointing to the tag tree mode of "historical". Is all of this normal behavior?

Edit: I believe it has to do with the Analog vs. Discrete deadband. Discrete seems to work like I'd expect....I'm having difficulty understanding exactly how the analog works.

2

I have a great fund of ignorance to draw from and my mental model1 is that the analog value is stored temporarily while a watch is kept to see if the value strays outside the deadband. When it does, a record is added to the historian.

For example.

5    start value
7    stored in temp (slope is +2)
9    temp updated (slope is +2)
11   temp updated (slipe is +2)
14   slope is +3 so store previous value, 11, in the historian
     temp is updated with 14
9    temp updated (slope is -5)
...

Edit: looking
For simplicity I've left out the deadband calculation (and because I would probably explain it incorrectly).

The manual page has been updated and, I think, explains it better than in previous versions - but I need to study it some more.

https://docs.inductiveautomation.com/display/DOC81/Configuring+Tag+History#ConfiguringTagHistory-DeadbandandAnalogCompression

1 "All models are false. Some are useful."

1 Like
3

Ah, ok, so the latest value is held in stasis and doesn't go into the historian until it deviates from the deadband. When that happens, that value is written and the new value is held in stasis until the deadband threshold is met. Am I mentally modeling that correctly?

4

That's essentially correct, yes (per the always winnowing, sliding window algorithm). You can also always force a record to be inserted with a max time between records on your tag group.

1 Like
5

Thanks everyone. Glad to know something in our system wasn't messed up.