Lachlan Macallan

I recently encountered a warning on a Prosonic Flow 300, titled S870 measurement inaccuracy. Upon further investigation the flow meter was operating close to or beneath its minimum flow velocity of 0.3 m/s (Gathered from the performance characteristics section of the operating manual). Personal communication with Endress and Hauser confirmed that the reason for this warning was likely due to the low flow velocity of the process at the time, and that their was some leeway in the warning which would explain why it was present even when the flow was just above the minimum parameter.

It was confirmed that this was the cause when the warning cleared after the process reached its normal operating flow rate.

Because in this context it was a nuisance warning I was asked by the client to configure the transmitter to prevent the warning from displaying again. This is a simple procedure if you would like to replicate it. Go to the expert menu > system > diagnostic handling > diagnostic behaviour, scroll to no. 870 and set it to logbook only.

This setting should be applied on a case by case basis. Endress and Hauser make sophisticated equipment and there will be an instance where this warning is relevant. In our situation the warning only displayed when the process was not flowing or coming to a stop, the flow meter was for information and metrics only and did not impact any safety systems, hence our decision.