Thermocouple sensors


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 NSPI 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)

NSPI Thermocouples

NSPI manufactures a broad variety of thermocouple components and assemblies for use in virtually all high temperature, industrial and process temperature measurement applications. Today, NSPI thermocouples are among the most widely used in the world for applications such as forging, smelting and melting, heat treating, incineration and cogeneration, utility and waste boilers and multiple other severe use processes. Many of our assemblies are supplied in either drilled or flanged wells, and all assemblies can be supplied with our economical, head mount or DIN-rail mounted transmitters. If you can’t find a catalog thermocouple for your application, just contact us – custom versions can often be fabricated in less than a week!

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
Data sheets
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
305 Ex d ATEX-Approved, flame-proof temperature sensor ATEX definitions (PDF)
305 Ex ia ATEX-Approved, intrinsically-safe temperature sensor assembly ATEX definitions (PDF)
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