ISA 5.1 cheat sheet PDF.
All 26 ISA 5.1 first letters, what each one measures, and the codes it most often takes. For the drawing table, when a tag prefix is unfamiliar.
- AAnalysis
- BBurner
- CUser's choice
- DUser's choice
- EVoltage
- FFlow
- GUser's choice
- HHand
- ICurrent
- JPower
- KTime
- LLevel
- MUser's choice
- NUser's choice
- OUser's choice
- PPressure
- QQuantity
- RRadiation
- SSpeed
- TTemperature
- UMultivariable
- VVibration
- WWeight
- XUnclassified
- YEvent
- ZPosition
All 26 first letters.
The first letter names what the instrument measures; the letters after it name what it does. User's-choice letters mean whatever the drawing set's own legend says.
| Letter | Measured variable | Common codes |
|---|---|---|
| A | Analysis | ATAIAICAEAAH |
| B | Burner, Combustion | BTBSBY |
| C | User's choice, commonly Conductivity | CTCICE |
| D | User's choice, commonly Density | DTDIDE |
| E | Voltage | ETEIEAH |
| F | Flow | FTFIFICFYFE |
| G | User's choice, commonly Gauging or Gas | GTGAHGSH |
| H | Hand | HSHVHIC |
| I | Current, electrical | ITIIIEIY |
| J | Power | JTJI |
| K | Time, time schedule | KYKI |
| L | Level | LTLILICLGLSH |
| M | User's choice, commonly Moisture | MTMI |
| N | User's choice | NT |
| O | User's choice | OT |
| P | Pressure | PTPDTPIPICPSV |
| Q | Quantity | QIQYQTQR |
| R | Radiation | RTRERAHRSH |
| S | Speed, frequency | STSISAHSSH |
| T | Temperature | TTTITICTETW |
| U | Multivariable | UTUI |
| V | Vibration, mechanical analysis | VTVEVAHVSHH |
| W | Weight, force | WTWI |
| X | Unclassified | XTXY |
| Y | Event, state, presence | YSYAH |
| Z | Position, dimension | ZTZIZSZSCZSO |
Watch the slot.
Six letters mean one thing first and another after it. Read the first letter first.
| Letter | As the first letter | As a succeeding letter |
|---|---|---|
| I | Current, electrical | Indicate |
| S | Speed, frequency | Switch |
| V | Vibration, mechanical analysis | Valve, damper |
| W | Weight, force | Well, probe |
| Y | Event, state, presence | Relay, compute, convert |
| D | User's choice, often density | Differential, as a modifier |
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.
We run it on your drawings.
The page is a reference you read at the drawing table. From your drawing set the register comes back built, each row traceable to the sheet it came from.