ABOUT
Introduction
Tempsens provides precision-made alloys for thermocouples that are engineered to deliver consistent EMF output regardless of the temperature across a wide temperature range. Each conductor is produced through strict adherence to compositional tolerances and provides excellent calibration stability for demanding industrial applications such as heat treatment furnaces, petrochemical reactors, power generation plants, and very low-temperature applications.
Tempsens thermocouple alloys meet IEC 60584 and ASTM E230 specifications for base metal and refractory metal thermocouples. Regardless of whether you require a low-cost general-purpose thermocouple wire, or a high-temperature nickel–molybdenum thermocouple for reducing atmosphere applications, Tempsens has the calibrated alloy pair available in bare wire, spooled, and extension-grade forms to meet your specific process requirements.
About Thermocouple Alloys
Thermocouple Alloy Specifications and Temperature Ratings
| Type | Conductor (*) Chemical Composition % | Conductor (-) Chemical Composition % | Temp range | American Standard ASTM E230/ANSI MC95.2 | European Standard IEC 584 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ni | Cr | Fe | Cu | Others | Cu | Ni | Others | T/c Range | Class 1 (0.4%) | Class 2 (0.75%) | T/c Range | Class 1 (0.4%) | Class 2 (0.75%) | ||
| K | 90 | 10 | – | – | – | – | 94 | Mn+ Si+ Others | -200°C to +1260°C | 0 to 1260°C | ±2.2°C | ±1.1°C | 0°C to 1260°C | ±1.5°C | ±2.5°C |
| N | 84.4 | 14.2 | – | – | Si 1.4 | – | 95.6 | Si4.4 | -200°C to +1260°C | 0°C to 1260°C | ±2.2°C | ±1.1°C | 0°C to 1260°C | ±1.5°C | ±2.5°C |
| J | – | – | 100 | – | – | Bal | 44 | Mn+ | -40°C to +760°C | 0°C to 760°C | ±2.2°C | ±1.1°C | 0°C to 760°C | ±1.5°C | ±2.5°C |
| T | – | – | – | 100 | – | Bal | 44 | Mn+ | -200°C to +370°C | 0°C to 370°C | ±1°C | ±0.5°C | 0°C to 370°C | ±0.5°C | ±1°C |
| E | 90 | 10 | – | – | – | Bal | 44 | Mn+ | -200°C to +870°C | 0°C to 870°C | ±1.7°C | ±1.1°C | 0°C to 870°C | ±1.5°C | ±2.5°C |
Thermocouple Types, Materials and Applications
| Thermocouple Type | Material + & – | Temp range | Application |
|---|---|---|---|
| E | Chromel & Constantan (Ni-Cr & Cu-Ni) | -200 to 900°C | Inert media, Oxidizing media |
| J | Iron & Constantan (Fe & Cu-Ni) | 0 to 750°C | Inert media, Oxidizing media, Reducing media Vacuum |
| K | Chromel & Alumel (Ni-Cr & Ni-Al) | -200 to 1250°C | Inert media, Oxidizing media |
| N | Nicrosil & Nisil (Ni-Cr & Ni-Si) | -270 to 1300°C | Inert media, Oxidizing media |
| T | Copper & Constantan (Cu & Cu-Ni) | -200 to 350°C | Inert media, Oxidizing media, Reducing media Vacuum |
Thermocouple Temperature Limits by Wire Size
| Type of thermocouple | Diameter | |||||
|---|---|---|---|---|---|---|
| 3.25 mm | 1.63 mm | 0.81 mm | 0.51 mm | 0.33 mm | 0.25 mm | |
| K | 1260°C | 1090°C | 980°C | 870°C | 870°C | 760°C |
| N | 760°C | 590°C | 480°C | 370°C | 370°C | 320°C |
| J | 1260°C | 1090°C | 980°C | 870°C | 870°C | 760°C |
| T | 350°C | 350°C | 260°C | 200°C | 200°C | 150°C |
| E | 870°C | 650°C | 540°C | 430°C | 430°C | 370°C |
Thermocouple Properties
- EMF output can change as temperature changes; it will be measured with the Seebeck coefficient
- Type E thermocouple alloys provide the best (although still confusing) Seebeck coefficients among base metals.
- Chromel-Alumel(type K) will give a linear response and will work in various industries.
- Type N alloys perform better than Type K (less drift) above 300°C due to the presence of ordered intermetallics.
- The resistivity of constantan is very stable, which is one reason for its popularity with several thermocouple types.
- Platinum alloys almost never oxidize and exhibit very stable long-term EMF.
- Tungsten-rhenium alloys are very brittle yet have no competitors for temperatures above 1800°C.
- All thermocouple alloys must be uniform to avoid spurious EMF from appearing along conductor cables.
- The initial calibration of thermocouples and the long-term drift characteristics will be influenced by the conditions under which the cold work and annealing process takes.
- The precision of alloy composition being controlled to within IEC specifications for output will be done by Tempsens.
Available Forms, Sizes and Quality Assurance
i) Available Forms – Wire, Rod and Bar in oxidized, acid wash and luster surface
ii) Available Diameters
- Standard range: 0.20 mm to 3.25 mm
- Custom diameters available on request for OEM requirements
iii) Quality Check and AnalysisEach spool and Coils is passed through proper testing and test certificates are provided for the following –
- Calibration Test
- Proof Stress Test
- Torsion Test
- Bend Test
- Hardness Test
- Tensile Strength Test
- Elongation
- Electrical Resistivity (Loop Resistance)
- Positive Material Identification(PMI) Test
- Accelerated Life Test
FAQ
Frequently Asked Questions
Find answers to frequently asked questions related to Thermocouple Alloys.
A Type C thermocouple has a positive leg made of Tungsten with 5% rhenium and a negative leg made of Tungsten with 26% rhenium. Both legs are suited for use in vacuum or inert atmospheres, and can function at temperatures up to 2315°C.
A Type K thermocouple’s positive leg is composed of Chromel (90% Nickel and 10% Chromium). The negative leg is made of Alumel (approximately 95% Nickel with Aluminium, Manganese and Silicon) and can be utilized between -200°C and +1260°C.
