All About Thermocouples

Feb 19, 2018 | Heating

Thermocouple and Pilot Flames in a Seattle Furnace

Thermocouples are sensors used to measure temperature. It is a device used inside your Seattle gas furnace, to assist the pilot light in keeping your furnace running and safe. It works rather like a fail-safe to keep unburned gas from accumulating and burning, exploding or causing another type of health risk.

A thermocouple consists of two wires, or wire legs, made from different metals. The legs are welded together at one end, into a junction, where the temperature is measured. A voltage is created when the junction senses a change in temperature. The voltage can then be interpreted using thermocouple reference tables to calculate the temperature.


There are many types of thermocouples. Different types are best suited for different applications. Usually they’re selected on a temperature-range and sensitivity-needed basis. Thermocouples are available in different combinations of metals or calibrations: base metal thermocouples, Types J, K, T, E, and N, are the most common; nobel metal thermocouples, Types R, S, C, and GB, are high-temperature calibrations. Call Ballard Natural Gas Service with any questions you may have about thermocouples. Our experienced technicians have the necessary knowledge and training to answer your questions.

Every calibration has a different environment and temperature range, though the maximum temperature is contingent upon the diameter of the thermocouple wire used. Therefore, a very thin thermocouple may not reach the full-temperature range. Because of its low cost and temperature range, the K type thermocouple is known as a general-purpose thermocouple.

Choosing a Thermocouple

Due to thermocouples measuring in wide temperature ranges and being comparatively rugged, they are often used in industry. When choosing a thermocouple, the following factors must be considered for the best result:

  • Determine the application where the thermocouple will be used.
  • Analyze the temperature ranges for the thermocouple exposure.
  • Assess any chemical resistance needed for the thermocouple or sheath material.
  • Evaluate the need to abrasion and vibration resistance.
  • List all, if any, installation requirements.

Thermocouples are usually selected based on their high-temperature limits, wide temperature ranges, low cost, and durable nature. They’re used in a wide range of temperature-measurement processes, typically science, industry, and OEM applications. Thermocouples are used in nearly all industrial markets, such as cement, oil/gas, power generation, biotech, and paper and pulp. They are also used in everyday Seattle home appliances like furnaces, toasters, and stoves.

If you are in Seattle or the greater Seattle area request service online and if you are not sure if you are in our service area, check out our service area page for more information on the communities we serve.

Ballard Natural Gas Service is proud to offer services to Seattle, Shoreline, West Seattle, Capitol Hill, Lake Forest Park, Richmond Beach, Bellevue, Mercer Island, Edmonds, Mountlake Terrace and the surrounding communities. Call us at 206-784-8101 or request service online today!

Share This


24-Hour Emergency Service Available