why the value of tag is comm fail.
I want to know that if the communication between pi interface and pi server failed or the communication between pi interface and dcs failed
Comm Fail error is related to the quality flag given by an OPC server when the quality of the data is bad. Following KB has more information.
Following KB article that lists and explains some of the more common digital error states,
thanks for your help.
Hello zhang feng,
Vasanth Kumar is exactly right. The most common cause is receiving bad values from the OPC DA Server. This can be traced via debug level 4096, selecting an afflicted tag and restarting the interface. This OPC DA level trace (not to be confused with UniInt tracing) will show the actual quality received from the OPC DA server. Should you be getting bad quality from the OPC DA server this likely means that the OPC DA Server / tunneler cannot communicate to the remote device. Normally this is not indicative of a health problem of the PI Interface to OPC DA server connection or the PI Interface to PI Data Archive connection.
thanks for your help
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