I have a calculation which I am performing on the PI server which I would like to write back to the OPC database. The calculation is being performed in the PI server by using a performance equation in the "exdesc" attribute of a PI point. Page 35 of the "PI Interface for OPC" manual states that the following changes need to be made to get a tag to write back to the OPC database:
- Location1 - Set to the ID perameter of the interface instance. What is this, is it the "pointid" of the tag I want to write back to the OPC server?
- Location2 - Set to 2.
- Instrumenttag - Is the OPC item to be written. I am assuming this is the name of the item I want to write the data to, the same as it is the item I want to extract the data from during normal instrument PI point configuration.
- Sourcetag - Is the PI point containing the value to be written. Does this mean that I can't complete my performance equation and write it to the OPC server using the same tag. I have to create a PI point for the sole purpose of writing data to the OPC server and reference "tag" attribute of my performance equation PI point in the "sourcetag" attribute of my PI point for writing back to the OPC server?
- Location 4 - Is set to 3 in the current performance equation PI point that I have configured. I don't really understand the description for this in the manual, do I need to change this value to get it to send data to the OPC server?