Max sample rate query tag


I have a question about a query tag. I have a MySQL database and a measurement device that refresh the value every 10 ms. Is it possible to connect a query tag to get a history? I have tried but I get not every sample.


Mitchel Gommers

Can you show your work so far? If you are missing samples, maybe they haven’t been inserted into the DB yet. Without giving more info, it’s hard to say.

Do you expect the historian to store value changes this fast? I have not tried to have historian storing that fast, 10 milliseconds seems a bit faster than I would consider supported.

Do you mean a ‘query’ tag? or rather an OPC tag that has history enabled?
A query tag is simply a tag that queries a table in a database. A query tag should return all results from your query and should never miss rows unless your query is wrong or you’ve limited the number of rows to return.

If you’re talking about an OPC tag with history enabled, that is connected to a PLC (or other similar device) to read your measurement device, then 10ms is an extremely fast sample rate. I’m not sure myself how fast Ignition can poll for data but I think you would be approaching its limit. It would also depend on the speed of your PLC and network capability as well.