User's Manual

Overview
Tag ID Breakdown
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Tag ID Breakdown
A Tag ID represents a functional specification and location of a device within a
process. The designated Tag ID for a device often contains this information (its
function and location), following standard Instrument Society of America (ISA)
instrument identification designations.
Consider the Tag ID value of PT-100. Per ISA, the first letter represents the
process variable of the Tag ID, which in this case is “P” for “Pressure”. The “T”
represents the function of the Tag ID, which in this case is “Transmitter”. The
“100” represents the loop this Tag ID is a part of. Thus, the Tag ID value of PT-
100 represents a pressure transmitter in Loop 100.
Common ISA designations for process variables include “T” for Temperature, “P”
for Pressure, and “L” for Level. Designations for Tag ID functions include “R”
for a Recorder, “I” for an Indicator, and “E” for an element, among others. There
are, in fact, several hundred possible combinations of designators that are used to
describe Tag IDs. While this might seem sufficient, far more detail is necessary to
precisely define the exact function of any given Tag ID. For example, a pressure
transmitter may be used to measure flow. To this end, DPC/TRACK is designed
to track information that truly specifies how a Tag ID fits into your overall
process.