Use the Instrument Symbols Legend CAD reference to identify instrument bubbles, measurement devices, tag abbreviations, and related control-diagram symbols in process documentation. It is intended as a practical companion for P&ID drafting, review, coordination, and commissioning work.
Because symbol conventions can vary by project, the drawing legend should be checked alongside the project drafting standard and instrument index. The downloadable DWG provides a reusable starting point for design teams working with instrumented piping and process systems.
This Instrument Symbols Legend CAD sheet is a detailed reference for P&ID and process drawings. It includes standard instrument bubbles, tag abbreviations, and common measurement device symbols—helping your diagrams remain consistent and easy to interpret for engineering, operations, and commissioning teams.
The legend typically covers:
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Instrument bubbles and locations (panel/central/local/behind control)
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Common tag types such as:
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Pressure: PI, PT, PR, PC, PIC, PRC
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Temperature: TI, TT, TR, TC
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Flow: FI, FT, FR, FC, FE
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Level: LI, LT, LR, LC, LA, LG
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Analyzer / transducer / specialty items
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Meter symbols and elements including orifice/venturi/v-cone, wedge meter, target meter, weir meter, ultrasonic meter, turbine meter, rotameter, vortex sensor, flow nozzle meter
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Accessories and drawing items such as quick change, straightening vanes, diaphragm meter, pitot tube/averaging pitot tube, thermometers, pressure gauges, connecting elements
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Simple logic items shown on the sheet (e.g., AND/OR/NOT gate symbols) where used in control diagrams
Use this CAD legend for:
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P&ID documentation sets and control schematics
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Standard symbol templates for drafting teams
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Training and QA review to avoid symbol/tag mistakes
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Faster instrument tagging and clearer drawings
How to use this instrument symbol legend
Start by using the instrument bubble and location notation to understand where an instrument is represented in relation to the process and control system. The sheet includes panel, central, local, and behind-control locations, which helps readers distinguish field devices from instruments represented at a control station or other display location.
Reading P&ID instrument tags
The listed tag groups cover pressure, temperature, flow, and level applications, along with analyzer, transducer, and specialty items. Treat these abbreviations as identification references rather than complete equipment descriptions. Confirm the intended function against the project instrument index, control narrative, datasheets, and loop documentation before using a tag in procurement or construction records.
For related drafting work, connect this reference with internal resources on P&ID terminology, pipe and fitting symbols, flange and valve identification, and CAD/DWG standards. Those references help maintain consistent linework, callouts, equipment tags, and piping connections across a drawing set.
Recognizing meter and sensing symbols
The legend includes flow-measurement elements such as orifice, venturi, V-cone, wedge, target, weir, ultrasonic, turbine, rotameter, vortex, and flow-nozzle meters. It also identifies accessories and sensing items including quick-change components, straightening vanes, diaphragm meters, pitot and averaging pitot tubes, thermometers, pressure gauges, and connecting elements.
These symbols communicate the type of device or sensing arrangement shown on a drawing; they do not by themselves establish a device rating, accuracy, material, calibration requirement, or installation detail. Use the applicable project documents and manufacturer information for those decisions.
Drafting and quality-control workflow
- Place the appropriate bubble and location notation before assigning or checking the instrument tag.
- Compare the symbol with the process line, equipment connection, and control function shown elsewhere in the P&ID.
- Check that repeated instruments use consistent abbreviations and graphic conventions.
- Review logic symbols, including AND, OR, and NOT gates, against the control narrative where they are used.
- Coordinate the final drawing with the instrument index, loop diagrams, and commissioning documentation.
This workflow supports clearer P&ID documentation, reusable drafting templates, training, QA review, and faster identification of symbol or tag inconsistencies.
Instrument Symbols Legend CAD FAQ
What is included in the Instrument Symbols Legend CAD file?
The reference includes instrument bubbles and locations, common pressure, temperature, flow, and level tag groups, meter symbols, sensing accessories, connecting elements, and simple logic symbols used in control diagrams.
Can this legend be used for P&ID drafting?
Yes. It can serve as a symbol reference and CAD template resource for P&ID documentation sets, control schematics, drafting coordination, and QA review. Project-specific drafting requirements should still govern the final drawing.
Does an instrument tag identify the complete device specification?
No. A tag and symbol identify the represented function or device category, but the complete specification should be verified in the project instrument index, datasheet, loop documentation, and other approved engineering records.
What types of flow meters are represented?
The sheet lists several meter and sensing arrangements, including orifice, venturi, V-cone, wedge, target, weir, ultrasonic, turbine, rotameter, vortex, and flow-nozzle meters.
Why are instrument locations shown on the legend?
Location notation helps readers understand whether an instrument is represented at a panel, central location, local location, or behind a control interface. This improves drawing interpretation and coordination between design, operations, and commissioning teams.