If you observer errors with Calculation collector, you should:
Procedure
Examine the collector log files in the Historian\LogFiles folder and scan for errors in the log that may explain your problem.
Check the connection to the source.
For example, if you lose connection to the source, all tags for that collector stop collecting. What that means is that even if you hard-code the formula results, the collector will not collect them. If you enter a formula such as result=7 on a polled, 1-second tag in the Server-to-Server Collector, Historian does not log any raw samples to the destination computer. This action occurs even though the result is hardcoded.