Type K Thermocouple Sensor Amplifiers with Cold Junction Compensation Using AD595-AD594

The sensor project is based on AD595 IC from Analog devices.  AD595 is a complete instrumentation amplifier and thermo-couple cold junction compensator on a monolithic chip. It combines an ice point reference with a pre-calibrated amplifier to produce a high level (10 mV/°C) output directly from a thermo-couple signal. Pin-strapping options allow it to be used as a linear amplifier-compensator or as a switched output set point controller. It is amplify its compensation voltage directly, thereby converting it to a stand-alone Celsius transducer with a low impedance voltage output. The AD595 includes a thermo-couple failure alarm that indicates if one or both thermo-couple leads become open. The alarm output has a flexible format which includes TTL drive capability.

NOTE : Refer AD595 Data sheet for supply input and other information, The circuit works with single supply, same board also support AD594 IC which can support type J sensor.


  • Supply 15V DC
  • Supports Type K Thermocouples
  • Provides 10 mV/Centigrade

Download PDF Schematic


What is Thermocouple??

A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor

What is Type K Thermocouple Sensor??

Type K Thermocouple (Nickel-Chromium / Nickel-Alumel): The type K is the most common type of thermocouple. It’s inexpensive, accurate, reliable, and has a wide temperature range. Type K thermocouples usually work in most applications as they are nickel based and exhibit good corrosion resistance. It is the most common sensor calibration type providing the widest operating temperature range. Due to its reliability and accuracy the Type K thermocouple is used extensively at temperatures up to 2300°F (1260°C). This type of thermocouple should be protected with a suitable metal or ceramic protection tube, especially in reducing atmospheres. In oxidizing atmospheres, such as electric furnaces, tube protection is not always necessary when other conditions are suitable; however, it is recommended for cleanliness and general mechanical protection. Type K will generally outlast Type J because the JP wire rapidly oxidizes, especially at higher temperatures.

Type K Thermocouple Range

  • Thermocouple grade wire, –454 to 2,300F (–270 to 1260C)
  • Extension wire, 32 to 392F (0 to 200C)


AD595 Output Voltages


Various Type K Temperature Sensors