T5R-T3R

Supported Applications

The Omega T5R/T3R series consists of unsheathed fine gage tungsten-rhenium thermocouples developed for measuring ultra-high temperatures in the 2760°C (5000°F) range. These sensors are designed specifically for use in hydrogen or inert gas atmospheres and vacuum environments.

Due to rapid deterioration under oxidizing conditions, these thermocouples should not be used in air or oxygen-containing atmospheres. The series supports three widely used calibrations: tungsten versus tungsten-26% rhenium (Type G), tungsten-5% rhenium versus tungsten-26% rhenium (Type C), and tungsten-3% rhenium versus tungsten-25% rhenium (Type D).

Operating Conditions & Performance

The series operates within a process temperature range of 0 to 425°C (32 to 800°F) and extends up to higher limits depending on wire diameter. For short-term exposure, the operating limit reaches 2760°C (5000°F). Accuracy is defined by two tiers based on temperature:

• ±4.5°C (±8°F) for temperatures from 0 to 425°C (32 to 800°F)
• ±1% of reading for temperatures above the lower range, extending up to specific maximums based on wire diameter

The upper temperature limit varies by wire size: 0.075 mm (0.003") wires are rated to 426 to 1750°C (800 to 3200°F); 0.125 mm (0.005") wires extend to 426 to 1975°C (800 to 3600°F) for Type C and D, or 426 to 1750°C (800 to 3200°F) for Type G; and 0.25 to 0.50 mm (0.010 to 0.020") wires extend to 426 to 2325°C (800 to 4200°F).

Configuration Options

The series is offered in unsheathed configurations with standard lengths of 300 mm (12"). Longer lead lengths are available upon consultation. The model number structure follows the format: <Materials>-<Wire Diameter mm (inch)>→<Model Number>, where the suffix indicates length in inches.

Available wire diameters include:

• 0.075 mm (0.003")
• 0.125 mm (0.005") and 0.127 mm (0.005") for Type D
• 0.250 mm (0.010")
• 0.381 mm (0.015")
• 0.500 mm (0.020")

Options and accessories include ceramic insulators and OMEGABOND® Cements (OB-Series). The tungsten versus tungsten-26% rhenium type is noted as more difficult to handle than the tungsten-5% rhenium versus tungsten-26% rhenium combination due to the brittleness of unalloyed tungsten. Ductility of W-3% Re is about equal to W-5% Re but superior to unalloyed tungsten.

Key Product Differences

The series distinguishes between three material combinations, each with specific handling characteristics and emf properties:

• Type G (Tungsten-Tungsten 26% Re): More difficult to handle due to unalloyed tungsten brittleness.
• Type C (Tungsten 5% Re-Tungsten 26% Re): Described as the most popular of the three, with a large selection of instrumentation available. Offers superior ductility compared to Type G.
• Type D (Tungsten 3% Re-Tungsten 25% Re): The average emf is slightly less than W/W-26% Re and slightly more than W-5% Re/W-26% Re. Ductility is about equal to Type C.