ISA 5.1 cheat sheet PDF.
An ISA 5.1 cheat sheet is a single printed page carrying the first letter of an instrument tag, which names what the instrument measures, alongside the succeeding letters that name what it does. It is what an engineer reaches for at a drawing table when a tag prefix is unfamiliar and the standard itself is two rooms away.
What the page carries.
A one-page reference card for ISA 5.1 first-letter conventions across all 26 letters. Common second letters and example tags for each. Print and tape it to the bid-room wall.
By Tagsight Team·Published Mar 27, 2026·Reviewed Sep 20, 2026
- Format.pdf
- Size5 KB
- Opens inAny PDF reader
What is on the page.
- All 26 first letters with meanings and example tags
- Common second-letter conventions noted per first letter
- Notes on user's-choice letters, C, D, G, M, N, O
- Watch-the-slot reminders for I, S, V, W, Y, D
- Print-ready Letter-size page
Common questions
What does the first letter of an ISA 5.1 tag mean.
It names the measured variable. F is flow, P is pressure, T is temperature, L is level. The letters that follow name the function: T for transmitter, I for indicator, C for controller, V for valve, S for switch.
What about the user's-choice letters.
C, D, G, M, N and O are left to the facility to assign, so the drawing's own legend decides them and the card says so rather than picking for you. The full reading guide covers the common assignments.
Is the card enough on its own.
For a quick prefix lookup at the drawing table, yes. For compound tags, modifier letters and how a tag becomes a signal class, the ISA 5.1 instrument identification guide walks through it line by line.
Related.
Run it on your drawings.
The page is a reference you read at the drawing table. Upload the drawing set instead and the register comes back built.
Three drawings included on a new account.