Platinum Composite Sheath Thermocouples

Platinum Composite Sheath Thermocouples enable flexible and responsive temperature measurement with a compact and cost-effective package design in environments where Base Metal Mineral Insulate Metal Sheathed cable would be unable to survive. Excellent option when an extended length probe is necessary but only a portion of the sheath length is exposed to extreme heat.

To achieve this Cleveland Electric Laboratories begins with two noble metal thermocouple wires that will each extend the full length of the thermocouple in one continuous piece. Crushable ceramic insulators are then threaded over the conductors. This insulation is typically made of high-purity Alumina but Hafnia or other insulations can also be used depending on the application and maximum usage temperature.

Separately a sheath is prepared. The length of the sheath that will see full temperature is made from Platinum or a Platinum/Rhodium blend. The remainder of the sheath is typically made of Inconel. These two sheath pieces are then fused together to create a seamless transition and the wire/insulator assembly is inserted into the sheath. The entire assembly is then prepared and compacted resulting in a longer and slightly thinner thermocouple wire free of any internal voids. The full assembly is then annealed to relieve any work stress and enable the greatest flexibility.

The hot end of the assembly is then junctions per specification and hermetically welded closed. The cold end is then terminated with exposed leads, industry-standard plug/jack or transitioned to soft wire.

The resulting assembly retains all the best qualities of the parts that it consists of with a significant cost reduction in comparison to a full Noble metal sheath. These assemblies are extremely flexible and may be bent to achieve small radii down to 4X the sheath diameter. The sheath materials have a high thermal conductivity to enable low-latency measurements and quick response times. The Noble metal sheath is also highly impervious to most chemicals and atmospheres while simultaneously highly resistant to mechanical and thermal shock. All of these qualities contribute to extended service life, exceptional accuracy and low drift.

All of CEL’s Platinum Composite Sheath Thermocouples are made to order. There are countless options in regard to combinations of wire Type, insulation, sheath material and finished size. All of these choices should be made after considering the temperatures involved, test time duration and other environmental factors such as shock, vibration and duty-cycle.

Seamless transition between differing sheath materials. Extreme temperature, highly accurate and flexible.

Applications for Platinum Composite-Sheath Thermocouples
Some unique applications require flexible thermocouples, with high-temperature materials across a short length of the sheath nearest the junction, but not across the entire length of the thermocouple. Composite sheath thermocouples, Type B, R or S, offer a Platinum alloyed sheath material on the hot-end with a seamless transition to standard Inconel sheathing for the remaining length. The overall build yields a finished product suitable for extreme temperatures only where your application requires. Our CST’s are designed to reduce overall cost without compromise in performance.


Gas Turbine Testing

Technical Data

Calibration: B, R & S
Sheath Diameters: .020 – .250
Termination: Multiple Termination Options
Certification: Individual or Lot Certification available upon request

Thermocouples for the Glass Industry

Temperature and purity are critical in the manufacturing of glass whether it is for labware, windows, beverage bottles or any of the thousands of ways glass is used in our daily lives. Thermocouples are used in every step of the glass manufacturing process including melting, refining, feeder channels, working end processing, testing as well as in combustion spaces and tooling temperature. Accuracy is important to produce the glass as well as in the machinery that processes it. In some instances, as low as a 2°F variation in the temperature can completely upset the operation of machines and render them inoperable. Replacement of thermocouples in areas that reach temperatures of 2700°F (1500°C) is not a pleasant task thus quality and long life are no less important than accuracy. All these attributes can be achieved though the use of high-quality components, applications-specific designs and best practices used in building thermocouples gained through years of experience.

In the combustion spaces and above the glass surface, or the crown, typical refractory materials can be used for insulators and protection tubes for the thermocouples. However, if these were to be used to measure the temperature of the molten glass itself, these sheath materials would be attacked and gradually dissolved. In these areas Platinum and Platinum/Rhodium alloys are necessary. Molten glass will not wet and stick to platinum and its alloys preventing it from adhering to the surface and affecting measurements and removal of the glass from the thermocouple in addition to protecting it from attack. CEL supplies platinum-coated protection tubes and pure platinum thimbles.

Cleveland Electric Laboratories has extensive experience working with glass manufacturers and creating designs that will provide the accuracy needed over a long life to minimize downtime and thermocouple replacement. We also have the same experience and relationships with our vendors to procure only the best components to build our thermocouples for optimal performance, purity, and reliability.

Custom-designed high-temperature thermocouple assemblies for use in the manufacturing of container & float glass.

Glass Immersion thermocouples, made with Type S, R or B conductors, are manufactured for robust, high-temperature applications. With a variety of insulating materials and outer protection tubes, our Glass Immersion product is designed to withstand long, in-service campaigns in the most rugged molten glass environment.


Fore Hearth, Melter Crown/Bottom/Side Wall, Regenerator Crown, Refiner, Distributor Sump, Spout, Throat, Glass Level & Glass Furnace

Technical Data

Calibration: B, R & S
Wire Gauge: 24 Gauge (Standard)
Protection Tubes: Alumina, Mullite, Silicon-Carbide, Re-Crystallized Silicon Carbide & Inconel
Special Prot. Tube/Coating: Platinum Thimble or Platinum Spray Coating
Termination: Multiple Termination Options
Hardware: Multiple Mounting Hardware Options

High Temperature Thermocouple Additional Services

  • Calibration & Certification Lab

  • Repair & Recalibration

  • Exchange Programs

  • Engineering Services

  • Value-added Services
  • Product Tagging & Serialization
  • Product Kitting

The Highest Standards in High Temperature Thermocouples

Unparalleled manufacturing, testing, and calibration services for superior accuracy and reliability.