Location5 (data handling for OPC HDA "Uncertain" data)

Location5 configures how the point will store OPC HDA data with the quality of Uncertain:

Note: The OPC HDA data can have a quality of Good, Uncertain, or Bad. If the quality is Bad, then the digital state Bad Input will be sent to Data Archive.

Quality information

The data values from the OPC HDA server have a quality value of either Good, Uncertain, or Bad. Because the Data Archive stores either the quality or the value, the interface will translate the qualities that are "Uncertain" to GOODSTAT, and set the "questionable value" parameter for the data value. This behavior can be changed on a point-by-point basis with the Location5 PI point attribute. Setting Location5=1 will cause the interface to store the digital state "Bad Quality" if the quality is "Uncertain." If Location5=2, the interface will ignore the "Uncertain" quality, and treat the value as if it had good quality. Note: if Location 5 is set to anything other than 0, 1 or 2, the interface will write an error message for that point and use the location 5 = 0 setting. The following table illustrates what is written to Data Archive for OPC HDA data of each possible quality for each of the valid values of Location5

You can also store the quality in a separate PI point, so both the values reported and also the qualities that came with those values are stored in Data Archive, with no loss of granularity. Setting Location2=1 for a point tells the interface to store the quality for the associated OPC HDA Item, rather than the value. Since OPC HDA qualities are unsigned, 32-bit integers, an Int32 PI point must receive them. The values are stored in PI without any change, and their status is always GOOD. To understand what those quality values represent, please go to http://www.OPCfoundation.org and download the OPC HDA Data Access specifications, which contain a brief discussion of quality data.