What is a Thermocouple?

A thermocouple can quantify temperature as it relates to a reference temperature. This reference temperature is usually sensed using a Thermistor, RTD or Integrated Silicon Sensor. The wide temperature range of the thermocouple makes it appropriate for many hostile sensing environments. A thermocouple consists of two dissimilar metallic wires that are connected at two different junctions, one for temperature measurement and the other for reference. The temperature difference between the two junctions is determined by measuring the change in voltage across the dissimilar metals at the temperature measurement junction. The International Society of Automation defines a number of commercially available thermocouple types in terms of performance. Type E, J, K and T are base-metal thermocouples and can be used to measure temperatures from about -200°C to +1000°C. Type S, R and B are noble-metal thermocouples and can be used to measure temperatures from about -50°C to +2000 °C.

Thermocouple Applications:

  • 􀂄Stoves
  • Engines
  • Thermopiles

Thermocouple Amplifier Circuit

The circuit below can be used for remote thermocouple sensing applications. The thermocouple is connected to the circuitry via a shielded cable and EMI filters. The thermocouple is tied to a positive and negative supply via large resistors so that the circuit can detect a failed open-circuit thermocouple.


The TC913A auto-zeroed op amp has been selected because of its low offset voltage of 15 μV (max) and high Common Mode Rejection Ratio (CMRR) of 116 dB (typical). Auto-zero and chopper amplifiers are good thermocouple amplifiers due to their low offset voltage and CMRR specifications. The cold junction compensation circuit is implemented with a TC1047A silicon IC temperature sensor located on the PCB.

20th Annual
Microchip MASTERs Conference 2016
Register now - Deadline: July 29

JW Marriott Desert Ridge Resort-Phoenix, AZ

© 2016 Microchip Technology, Inc.
Information contained on this site regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer's risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights.