Unified Automation Forum

Is It possible for data logger to write timestamps with bad status. I see that it is logging number of messages with BadStatus but they are not written to the file. I understand that values with bad status shouldn't be used in analysis, but different bad status codes might be might be useful to indicate data loss, bad quality or other errors. So one might want it to be accessible for the client.

Hi,

the current data logger implementation in UaExpert only writes to file when "value" was received. In OPC UA it is not allowed to provide value when StatusCode is "bad" (value must be null). Only when StatusCode is "uncertain" (or good) a value will be provided, and data logger plugin is writing the value into the csv file, including the status code. The current data logger implementation in UaExpert tries to persist a very compact file (only when having value).

So yes, you should not use "bad" values in analysis, however you can't anyway because a compliant server will not provide any "bad" values. You should look into the status code to decide what to do with the "uncertain" values. The status code makes more sense for a GUI tool or some diagnostic tool, a simple and poor data logger as in UaExpert, will look into values only.

Secondly I am not sure that "bad" status is really indicating data loss. It is more indicating an error at the source (and the reason thereof). But from an OPC UA perspective there was no data, instead a data loss is detected with sequence numbering in publish response and corresponding message acknowledgement (all observed internaly by the Unified Automation SDK).