InstrumentTag

If the source tag name length exceeds 80 characters, users must use the UserInt1 attribute for source point mapping. This is due to a limitation with the PI API programming library which supports tag names of 80 characters or less for point ID resolution.

Length

Depending on the version of the PI API and the Data Archive, this interface supports an InstrumentTag attribute whose length is at most 32 or 1023 characters. The following table indicates the maximum length of this attribute for all the different combinations of PI API and PI Data Archive versions.

If the PI Data Archive version is earlier than 3.4.370.x or the PI API version is earlier than 1.6.0.2, and you want to use a maximum InstrumentTag length of 1023, you need to enable the PI SDK. See ***PI SDK Options for information.

Source tag name

Unless the /tn, /tnex, or /ptid interface parameter is used, the InstrumentTag can be used to specify the name of the source tag. The ExDesc and Tag attributes can also be used for source tag name definition (see below). The UserInt1 attribute can be used to specify the source tag by point ID instead of tag name. The How the PI to PI Interface finds source points section explains how the interface parameters affect which receiving tag attributes are used for mapping to the source point and the order that the attributes are searched for a mapping.

The interface checks the InstrumentTag attribute first. If the InstrumentTag is empty, the extended descriptor is checked for STAG=< tagname > at the beginning of the ExDesc value. That is, the ExDesc attribute must begin with the ' STAG' keyword. If neither InstrumentTag nor ExDesc has a tag name, the UserInt1 attribute is checked for the source tag point ID. Finally if none of these three attributes identify a source point, the receiving tag name is used for the source tag name.