Temperature transmitter symbol

An instrument bubble tagged for temperature transmission.

Also known as: TT instrument symbol, Temperature measurement transmitter

Engineering & technicalStandard profile

Meanings

On a piping and instrumentation diagram a bubble tagged TT denotes a temperature transmitter, converting a sensor reading into a transmitted signal.

Officially standardisedVerified fact
Denotes an instrument converting a temperature sensor reading into a transmitted signal.
Contexts: Technical drawing
Common modern usageVerified fact
Is drawn connected to a thermowell rather than directly to the process, because a sensor is normally removable without breaching containment.
Contexts: Technical drawing

An instrument circle containing the letters T and T above a loop number, connected to a thermowell on the process.

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

ISA-5.1: Instrumentation Symbols and Identification
International Society of Automation · retrieved 2026-08-24
The standard governing instrument bubbles, tag letters and signal-line conventions on piping and instrumentation diagrams. Cited for what each symbol and letter denotes. Sold rather than published openly.
Piping and instrumentation diagram
Wikipedia · retrieved 2026-08-23
Tertiary reference, cited for the conventional description of a mark, its usual name and where it is encountered. Where an issuing body defines the mark, that body is cited alongside and governs.
ISO 10628: Diagrams for the chemical and petrochemical industry
International Organization for Standardization · retrieved 2026-08-24
Defines the equipment symbols used on process flow and piping diagrams — vessels, exchangers, pumps, columns and the rest of the plant inventory. Sold rather than published openly; cited for what a symbol denotes rather than quoted.

Last reviewed 2026-08-24

Meanings

On a piping and instrumentation diagram a bubble tagged TT denotes a temperature transmitter, converting a sensor reading into a transmitted signal.

Officially standardisedVerified fact

Denotes an instrument converting a temperature sensor reading into a transmitted signal.

Common modern usageVerified fact

Is drawn connected to a thermowell rather than directly to the process, because a sensor is normally removable without breaching containment.

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

ISA-5.1: Instrumentation Symbols and Identification
International Society of Automation · retrieved 2026-08-24
The standard governing instrument bubbles, tag letters and signal-line conventions on piping and instrumentation diagrams. Cited for what each symbol and letter denotes. Sold rather than published openly.
Piping and instrumentation diagram
Wikipedia · retrieved 2026-08-23
Tertiary reference, cited for the conventional description of a mark, its usual name and where it is encountered. Where an issuing body defines the mark, that body is cited alongside and governs.
ISO 10628: Diagrams for the chemical and petrochemical industry
International Organization for Standardization · retrieved 2026-08-24
Defines the equipment symbols used on process flow and piping diagrams — vessels, exchangers, pumps, columns and the rest of the plant inventory. Sold rather than published openly; cited for what a symbol denotes rather than quoted.

Last reviewed 2026-08-24