Instrument tag

When a value is retrieved from or sent to an external system such as a Distributed Control System (DCS), the instrument tag is used by some interfaces as the tag in the external system. The InstrumentTag field can be any length. However, most interfaces only use the first 32 characters of this attribute. There is no limitation for special characters for instrument tag. Some interfaces use the extended descriptor (ExDesc) instead.

For more details see Introduction to the PI to PI Interface.