I - Current, electrical
Reference for the ISA 5.1 first letter I. Watch what slot the I sits in. First-letter I means current, IT, II. Second-letter I means indicator, FI, PI, LI. When a junior engineer reads IT-505 as 'indicator-transmitter' the meaning flips. They hunt for an analog input where there's actually a current measurement coming from the electrical scope. Parse the first letter first.
Read one of your own drawings.
Drop a P&ID, instrument index, or schedule. Tagsight reads it to the tag and opens a workspace you keep when you sign in.
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Also stands for.
- Modifier. Indicator, when used as a second letter, e.g. FI, PI
Common second letters.
Transmitter, IT. Current transmitter, e.g. Motor amp meter
Indicator, II. Current indicator
Sensor, primary element, IE. Current sensing element, e.g. A current transformer
Computing, relay, IY. Current relay or signal converter
Example tags.
Current transmitter, often a motor-current monitor brought into the BPCS
Current indicator, ammeter
Current sensing element, the current transformer feeding the transmitter
Typical placement.
On electrical signals brought into the process control system. Motor current to detect bearing wear or overload, transformer current for utility-side metering. Like E-prefix tags, I-prefix tags are uncommon on a process P&ID because most electrical measurement lives on a separate electrical drawing set.