# D — Thermocouple type letter to alloy pair, ANSI/IEC color code and tolerance class

For D, usable temperature range is 0 to 2320°C; source document is ANSI and IEC Color Codes, verified against its source on 2026-08-19.

- **Type letter:** D _(verified: appears in the quote below)_
- **Usable temperature range:** 0 to 2320°C _(verified: appears in the quote below)_
- **Source document:** ANSI and IEC Color Codes _(verified: appears in the quote below)_

## What the source says

> D* D Vacuum, Inert, Hydrogen. + TUNGSTEN- TUNGSTEN- Beware of Embrittlement. Not Practical Below NO STANDARD NONE 0 to 2320°C USE ANSI – 3% RHENIUM 25% RHENIUM 399°C (750°F)–Not for ESTABLISHED W-3% Re W-25% Re 32 to 4208°F 0 to 39.506 COLOR CODE (W3) Oxidizing Atmosphere (W3)

## Source

- https://assets.omega.com/pdf/test-and-measurement-equipment/temperature/sensors/thermocouple-probes/tc_colorcodes.pdf

Last verified: 2026-08-19. Review by: 2028-08-18.
Part of [Thermocouple type letter to alloy pair, ANSI/IEC color code and tolerance class](https://referencesource.org/thermocouple-type-color-code-crosswalk/).