Thermocouples

Thermocouples measure temperature based on voltage potential. They consist of two dissimilar electrical conductors that are joined in electrical junctions. When the junctions are at different temperatures, it produces a temperature-dependent voltage as a result of the thermoelectric effect, and you can interpret this voltage to measure temperature.

Durex Industries manufactures reliable and robust industrial thermocouple sensors. Thermocouples provide fast temperature response that can be applied in most temperature measurement and control applications. We are prepared to provide the best thermocouple temperature sensor solutions.

How Thermocouple Sensors Work

A thermocouple junction is a single point junction between two dissimilar metals.  This junction creates a known millivolt level signal that changes as the process temperature increases or decreases. The millivolt signal is used as the temperature measurement input to a temperature controller.

Depending on an application's process temperature range, accuracy specifications, and material compatibility, our sensors are available in Type K thermocouples, Type J thermocouples, Type E thermocouples, Type T thermocouples, Type S thermocouples, Type R thermocouples, and other dissimilar metal combinations. Durex Industries manufactures thermocouple temperature sensors that can be designed with grounded or ungrounded junctions and housed in insulated sheath materials that are designed for best form fit in the applications.

Considerations When Deciding Between Grounded and Ungrounded Junctions

Grounded thermocouple junctions physically touch the metal sheath of the temperature probe, and they are electrically grounded. This physical connection gives them a faster response time, but it can also make them susceptible to electrical noise. These stray voltages can interfere with the accuracy and control of measurement.

Ungrounded thermocouple junctions, however, are not susceptible to electrical noise issues because there is no physical or electrical contact between them and the metal sheath of the temperature probe. This lack of contact does reduce the response time to temperature changes, however.

Custom Thermocouple Temperature Sensors

Durex Industries has been engineering and manufacturing quality custom thermocouples for over 40 years. Our engineering team will assist you with a thermocouple sensor design that fits your application requirements.

Ask us how we can help you with your OEM product roll-out. To learn more about our thermocouple sensors and how Durex can help you, contact us today.

Need help deciding which type of temperature sensor is right for your application, view our temperature sensor element selection guide.
----Mineral Insulated Thermocouples

Mineral Insulated Style

Mineral insulated temperature probes are manufactured with compacted magnesium oxide (MgO) insulation housed in a stainless steel or alloy sheath that protects the thermocouple element from the application's environment.

----Melt Bolt Thermocouple Probes.jpg

Adjustable Melt Bolt Style

Adjustable melt bolt thermocouple probes have a movable probe activated by an inner screw mechanism. The probe can be immersed into or withdrawn from the plastic melt stream while the extruder is in full operation at maximum flow rates and pressures.

----Adjustable Depth TC Probe with Armor TBA20.jpg

Adjustable Thermocouples

Adjustable depth thermocouples are used in plastics extrusion equipment and other industrial applications where robust temperature sensor probes are required.

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Base Metal Protection Tube Thermocouples

Protection tube thermocouples are designed to be used in non-pressure environments such as industrial ducts, flues, and heat treating ovens.

Base Metal Thermowell Thermocouple Assemblies

Base Metal Thermowell Assemblies

Thermowell thermocouples are manufactured from drilled bar stock and have threaded NPT process connections or flanges for direct immersion into high pressure or corrosive applications.

Compression-Fitting-Thermocouples

Compression Fitting Style

Compression fitting thermocouple probes are typically used in plastics, packaging, and other industrial sensing applications requiring robust sensor solutions.

Diesel Engine Sensors

Diesel Engine Temperature Sensors

Temperature monitoring in today’s sophisticated engines is critical for proper engine control module (ECM) operation to ensure high fuel efficiency and low emissions levels in diesel engines, extreme racing vehicles and aircraft jet engines. Our RTDs, Thermocouples, IC sensors and Thermistors are specifically designed to perform in rugged harsh environments.

 

Fixed Bayonet Thermocouples

Fixed Bayonet Style

Fixed bayonet thermocouple probes s are available in a wide variety of lengths, mounting configurations and styles.  Standard options include 304 stainless steel probe construction with flexible stainless steel cable lead wire protection.

----General Purpose Thermocouples

General Purpose (Tube & Wire) Style

General purpose thermocouple probes are economical sensor assemblies that usually consist of a soft insulated fiberglass or Teflon wire that is housed in a stainless steel tube.

Melt Bolt Thermocouples

Melt Bolt Style

Melt bolt temperature probes are designed for dependable temperature measurement of the plastic melt stream within extruders and injection molding equipment. Supplied with mineral insulated (MgO) sensing elements for extended pressure and temperature performance.

----Miniature Thermocouples.jpg

Miniature Thermocouples

Durex manufactures a complete line of miniature thermocouple temperature probes for applications with tight space requirements, limited access or other considerations.

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Multipoint Style

Multipoint thermocouple temperature probes are designed specifically for pipelines, process towers, boilers and other vessels where multi-point temperature monitoring is a must.

----Nozzle Thermocouples

Nozzle Style

Nozzle thermocouple sensors are used for mounting requirements on a plastics injection equipment, hot runner molds, and other auxiliary apparatus.

----Pipe Clamp Thermocouples TPC1 Style

Pipe Clamp Style

Pipe clamp thermocouples for temperature measurements on pipe ranging from ½" to 2-1/4" diameters. Stainless steel over-braid shield protects the element, which senses the temperature on the surface of the clamp.

Platinum Thermocouples

Platinum (Noble Metal) Style

In high temperature and corrosive environments, Durex' noble metals, also called platinum, probe assemblies are designed for greater robustness and accuracy than can normally be achieved with base metal thermocouples.

----Shim Stock Thermocouples.jpg

Shim Stock Style

Shim stock thermocouple sensors are available in Type J or Type K calibration with various junction types. Several lead wire types to choose from in lengths up to 24 ft.

Silicon Carbide Protection Tube Assembly-2

Silicon Carbide Protection Tube Assembly

Silicon carbide protection tube sensor assemblies feature a silicon carbide protection tube along with an inner ceramic tube for additional protection of the sensing element.

----Surface Mount Thermocouples TSM Style

Surface Mount Style

Thermocouples for surface mounting via ring lug or gasket. Applications include semiconductor equipment, life science instrumentation, medical devices and other industrial applications.

Durex offers testing at standard temperatures for determination of initial calibration tolerances for thermocouples. All calibration tests are fully traceable to the National Institute of Standards and Technology (NIST). Calibration is also available for application temperatures other than the standard points in a range from -100°F to 3000°F (-79°C to 1650°C) depending on material. Certificates are supplied for all items calibrated.

 

Thermocouple Calibration

Calibration (T/C Type) Temperatures Available Applicable Specifications
Type E, J, K, T Thermocouples 32°F to 2300°F(0°C to 1250°C) ASTM E 207 / ASTM E 220
Type R, S Thermocouples 32°F to 3000°F(0°C to 1649°C) ASTM E 230 / ANSI MC 96.1
Type E, K, T Thermocouples -320°F & -110°F to 23°F(-196°C & -79°C to 0°C)


Durex manufactures thermocouple assemblies in the following calibration options.

ANSI Letter Durex Code and Calibration Calibration Description
Type E Thermocouple E / Chromel P-Constantan Standard Limits 32°F to 1652°F (0°C to 900°C) 1.7°C or 0.5% Tol.
Special Limits 32°F to 1652°F (0°C to 900°C) 1.0°C or 0.4% Tol.
Type J Thermocouple J / Iron - Constantan Standard Limits 32°F to 1382°F (0°C to 750°C) 2.2°C or 0.75% Tol.
Special Limits 32°F to 1382°F (0°C to 750°C) 1.1°C or 0.4% Tol.
Type K Thermocouple K / Chromel P-Alumel Standard Limits 32°F to 2282°F (0°C to 1250°C) 2.2°C or 0.75% Tol.
Special Limits 32°F to 2282°F (0°C to 1250°C) 1.1°C or 0.4% Tol.
Type T Thermocouple T / Copper-Constantan Standard Limits 32°F to 662°F (0°C to 350°C) 1.0°C or 0.75% Tol.
Special Limits 32°F to 662°F (0°C to 350°C) 0.5°C or 0.4% Tol.
Type R Thermocouple R / Pt 13% Rhodium-Platinum Standard Limits 32°F to 2642°F (0°C to 1450°C) 1.5°C or 0.25% Tol.
Special Limits 32°F to 2642°F (0°C to 1450°C) 0.6°C or 0.1% Tol.
Type S Thermocouple S / Pt 10% Rhodium-Platinum Standard Limits 32°F to 2642°F (0°C to 1450°C) 1.5°C or 0.25% Tol.
Special Limits 32°F to 2642°F (0°C to 1450°C) 0.6°C or 0.1% Tol.

Thermocouple Sheath Diameter Specifications

Sheath Code T Y W A B V C D E F H
Sheath Diameter .020" .032" .040" .062" .125" .156" .188" .250" .313" .375" .500"
Wire Gauge 38 34 33 30 24 22 20 18 16 15 11
Maximum Length 100' 150' 200' 400' 250' 200' 175' 100' 55' 40' 30'


Thermocouple Specifications

Sheath - Tolerances: Outside diameter ± 0.002” of nominal size.

Finish - Bright annealed, 32 micro-inch or better.

Insulation - High purity magnesium oxide is standard; ultra high purity magnesium oxide and alumina oxide are available.

Configurations - Sheath diameters available from 0.020" to 0.500". Two wire (single circuit) and four wire (double circuit) configurations are standard in most diameters.

Formability - Minimum radiums: 2X sheath diameter for most thermocouple materials. Consult Durex Industries if special forming is required.

Weldability - Thermocouple sheath can be brazed, soldered, or welded without loss of insulation resistance. Welding of special sheath materials by the customer is not recommended.

Physical Testing

  • Dimensional and visual
  • Helium leak
  • Radiographic (X-Ray)
  • Dye Penetration
  • Metallurgical per ASTM E-2, E-3, and E-112
  • Compaction density per RDT C2-IT

Electrical Testing

  • Calibration per ASTM E-220 traceable to NIST
  • Insulation resistance
  • Wire resistance (ohms per foot loop)
  • Time response per RDT C2-3T
  • Thermal cycling per ASTM E-225

ASTM Testing - Sheathed thermocouple material and sheathed thermocouples are tested using the following specifications:

  • ASTM E585     Standard specifications for sheathed based-metal thermocouple materials.
  • ASTM E608     Standard specifications for metal-sheathed base-metal thermocouples.
  • ASTM E780     Standard method for measuring the insulation resistance of sheathed thermocouple-material at room temperature.
  • ASTM E839     Standard test methods for sheathed thermocouples and sheathed thermocouple material.
Insulation Resistance

Nominal Sheath Outside Diameter

Applied D.C. Voltage (min.)

Insulation Resistance MegΩ

.030” Diameter and smaller

50

ASTM E 207 / ASTM E 220

.030” Diameter and smaller

50

ASTM E 230 / ANSI MC 96.1

.062” Diameter and larger

500

1000

Custom Options Available - Contact us for Engineering Assistance.

Applications for Industrial Thermocouples

Thermocouple sensors are used in a wide variety of applications.  They can be used in cryogenic temperatures to molten steel above 1500C.”

You can commonly find industrial thermocouples in:

  • Metals Processing (Aluminum, Steel, and other metals)
  • Ovens, Furnaces, Kilns
  • Plastic Processing
  • Food Processing and Preparation
  • Chemical and Petro-Chemical Processing
  • Pulp & Paper Mills
  • Power Generation Plants
  • Engines

Thermocouple Wire Code Standards

Color-codes have been adopted by various national and international standard agencies for identification of thermocouple wire and thermocouple products. In the United States, thermocouple grade wire normally has a brown overall jacket. For Types B, R, and S the color-codes relate to the compensating cable normally used.

 

Type United States
ANSI 96.1
United Kingdom
BS 1843
Germany
43714
France
NF C42-323
Japan
JIS C1610-1981
E Purple
+ Purple
- Red
Brown
+ Brown
- Blue
Black
+ Red
- Black
Purple
+ Red
- White
J Black
+ White
- Red
Black
+ Yellow
- Blue
Blue
+ Red
- Blue
Black
+ Yellow
- Black
Yellow
+ Red
- White
K Yellow
+ Yellow
- Red
Red
+ Brown
- Blue
Green
+ Red
- Green
Yellow
+ Yellow
- Purple
Blue
+ Red
- White
N Orange
+ Orange
- Red
B Grey
+ Grey
- Red
Grey
+ Red
- Grey
Grey
+ Red
- White
R Green
+ Black
- Red
Green
+ White
- Blue
Black
+ Red
- White
S Green
+ Black
- Red
Green
+ White
- Blue
White
+ Red
- White
Green
+ Yellow
- Green
Black
+ Red
- White
T Blue
+ Blue
- Red
Blue
+ White
- Blue
Brown
+ Red
- Brown
Blue
+ Yellow
- Blue
Brown
+ Red
- White

 

Contact us for Engineering Assistance.

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