Thermocouples for Factory & Mill


A thermocouple consists of two dissimilar metals, joined together at one end. When the junction of the two metals is cooled or heated a voltage is produced that can be correlated back to the temperature. Most thermocouple alloys are commonly available as wire.

Thermocouples are manufactured in different combinations of metals and/or calibrations. The calibrations most regularly specified by Ultra’s customers are J, K, T and E. High temperature calibrations include R, S, C and GB. Each calibration has a different temperature range and environment, although the maximum temperature varies with the diameter of the wire used in the thermocouple.

While the thermocouple calibration defines the temperature range, the maximum range will also be a factor the diameter of the thermocouple wire. Therefore, a very thin thermocouple may not reach the full temperature range.

Since thermocouples measure wide temperature ranges and are relatively rugged, they are very often used demanding industrial automation and process control applications. In selecting a thermocouple, the following criteria are key considerations:

  • Temperature range
  • Chemical resistance of the thermocouple or sheath material
  • Abrasion and vibration resistance
  • Installation requirements (may need to be compatible with existing equipment;existing holes may determine probe diameter)

Typical thermocouple applications

  • Test stands
  • Medical equipment
  • Aerospace markets
  • Packaging equipment
  • Semiconductor processing
  • Food processing equipment
  • Heat treating and processing
  • Engine and turbine exhaust gas
  • Plastic injection molding machinery
Model (PDF) Description
101 & 103 General purpose
110 Field cuttable
120 Hand-breakable
201 & 203 With welded fittings
301 Spring loaded for use with cast iron explosion-proof housings
302 Spring loaded without transmitter for general purpose housing
305 Spring loaded, 1/2″ NPT hex hipple
312 Spring loaded (for use with type 1 general purpose head)
452 Spring loaded sanitary temperature sensor
3142B Sanitary flush mount tank temperature sensor
3226A Food piercing temperature sensor
3304A Flexible stick-on surface temperature sensor
3312A Autoclave temperature sensor
3332A Embedded temperature sensors for rotating machinery and turbines
Bearing temperature Sensors for the measurement of bearing temperatures
Bayonet fitting design Spring loaded bayonet fitting temperature sensors


Thermocouple General Specifications

Thermocouple Reference Tables

How to Size a Sensor


Mineral Insulated (MgO) thermocouple assemblies are metal sheathed, magnesium oxide insulated temperature sensing elements. These small, compact units are moisture proof, non-porous, and pressure resistant. They are available with single or dual elements and are noted for accuracy and fast response. These thermocouple assemblies come in a large variety of sheath materials and calibrations. Installation is made easier because Mineral Insulated thermocouple assemblies are bendable to practically any contour. The metal sheath is made of durable alloys and can be welded. These thermocouple assemblies have consistency that is assured by excellent quality control in manufacturing.

Key selection criteria:

  • What is the temperature Range Required?
  • What is the Thermocouple Type?
  • What Connection Type?
Model Configuration
701 MgO – Plain Stripped Ends
716 MgO – Standard Plug
718 MgO – Heavy Duty Plug
721 MgO – Standard Jack
723 MgO – Heavy Duty Jack
751 MgO – Steel Plug & Aluminum Screw Cover Head
753 MgO – Steel Plug & Cast Iron Screw Cover Head
761 MgO – 1/2″ x 1/2″ Hex Fitting & Aluminum Screw Cover Head
763 MgO – 1/2″ x 1/2″ Hex Fitting & Cast Iron Screw Cover Head
782 MgO – Thermocouple w-Extension Leads, Bare Strip
783 MgO – Thermocouple w-Extension Leads w-Plug
784 MgO – Thermocouple w-Extension Leads w-Jack
785 MgO – Thermocouple w-Stainless Steel OverBraid Extension Leads, Bare Strip
786 MgO – Thermocouple w-Stainless Steel OverBraid Extension Leads w-Plug
787 MgO – Thermocouple w-Stainless Steel OverBraid Extension Leads w-Jack
792 MgO – Thermocouple w-Flex Armor Extension Leads, Bare Strip
793 MgO – Thermocouple w-Flex Armor Extension Leads w-Plug
794 MgO – Thermocouple w-Flex Armor Extension Leads w-Jack

Nobel Metal Thermocouple Elements

All elements are provided to match the ITS 1990 curve.  24 ga. (0.020″) wire is standard – other gauges are available.  Spools of bare platinum wire are available. 

Alumina is recommended above 2400ºF and is supplied as a standard. Mullite causes silica contamination of the platinum element above this temperature.  Fishspine insulators and copper sleeves are supplied as standard termination.  Standard insulator = 3/16″ O.D. and 1/16″ bore.   Other diameters available.  A collar should be used in all vertical applications.

Model Configuration
25X Bare Wire Element
26X Insulated Wire Element
27X Insulated W-Collar Wire Element


Noble Metal Thermocouple Assemblies


Noble Metal thermocouple assemblies consist of a Platinum or Tungsten Rhenium Elements with a protection tube(s) and a termination head.  Elements are Types R, S, B and C and are available with Ceramic, Inconel, Stainless Steel, Molybdenum Protection tubes in standard and customer lengths. Termination heads are available in aluminum & cast iron screw covers and also in various open terminal heads.


Model Configuration
591 Nobel Metal – Open Terminal Head
592 Nobel Metal – G7 Open Terminal Head
593 Nobel Metal – Screw Cover Head w-Nipple
594 Nobel Metal – Screw Cover Head w-Hex Fitting
595 Nobel Metal – Open Terminal Head – w-SiC & Support Casting Assembly
596 Nobel Metal -Screw Cover Head – w-SiC & Support Casting Assembly
597 Nobel Metal -Screw Cover Head – w-SiC & WeatherProof Cover Assembly


Vacuum Thermocouples

Vacuum thermocouples are designed for use in vacuum furnaces and other applications requiring high temperature measurement in controlled atmospheric conditions. Our high temperature thermocouples generally operate in a temperature range of 1800ºF. (982ºC), through 4200ºF. (2300ºC). The construction style consists of a high purity alumina (or Hafnia) insulated 24 gauge element inside Alumina, Molybdenum, or Inconel sheath with a plug. Many are argon back filled and sealed for use in vacuum applications. Special drawings and construction designs can also be made to meet customers needs.


Base-Metal-Thermocouple-ElementsBase Metal Thermocouples

Base Metal Thermocouple Elements, Ceramic Insulators, Metal Protection Tubes and other Base Metal Thermocouple Hardware and Supplies. Standard calibrations include E, J, K, N and T. Available in a wide variety of wire gauges, lengths and configurations – customized to your specifications. Contact us with your requirements.


Model Configuration
1XXY Base Metal – Bare Wire Element (XX = Wire Gauge 8,11,14,20, Y=Type J,K,N,etc)
2XXY Base Metal – Insulated Wire Element (XX = Wire Gauge 8,11,14,20, Y=Type J,K,N,etc)
3XXY Base Metal – Angled Insulated Wire Element (XX = Wire Gauge 8,11,14,20, Y=Type J,K,N,etc)
Straight Base Metal – Assembly w-Protection Tube  Head


Nonferrous Molten Metal Thermocouple Tips and Lance Handles

Nonferrous Molten Metal Thermocouple Tips are designed for intermittent temperature sensing below 2300°F for use in molten brass, copper, aluminum lead and other nonferrous metals.  They are available in a variety of tip lengths.  Lance Handles are available Curved, Angled, or Straight.  Contact us today with your requirements, and we will be delighted to assist.

For Use w-Covered Lance Handle
Part # X Length Y Length Length Part #
MT-8-Y 8″ 36″ 31″ LH-31
MT-12-Y 12″ 49″ 43″ LH-43
MT-15-Y 15″ 61″ 55″ LH-55
MT-20-Y 20″ 79″ 72″ LH-72
MT-24-Y 24″ 103″ 96″ LH-96