All About Pyrometers

Written by
The MurCal Blogster
Published on
September 2, 2022 at 3:13:00 PM PDT September 2, 2022 at 3:13:00 PM PDTnd, September 2, 2022 at 3:13:00 PM PDT


Pyrometers are remote-sensing thermometers used to measure the temperature of distant objects based on their incandescence, which is emitted by hot objects. The word pyrometer comes from two Greek words: pyr, meaning fire, and meter, meaning measure. 

Pyrometers are also known as “Infrared Thermometers”, “Radiation Thermometer” or “Non-Contact Thermometers”, and they absorb energy and measure the intensity of electromagnetic waves.

A pyrometer consists of two parts: a thermocouple and a galvanometer.

In thermocouples, a small electric current is generated when two dissimilar metals are heated where they join. Because the galvanometer measures current in millivolts, it is actually a millivolt meter.


Probably the earliest known pyrometer is the “Hindley Pyrometer” in the London Science Museum, dating from 1752 and produced for the Royal Collection. During the 1760s, the Swiss mathematician Leonhard Euler described the pyrometer in some detail. Mathematicians consider Euler the greatest of the 18th century and among the greatest in history.

The English potter Josiah Wedgwood invented a different type of pyrometer to measure the temperature in his kilns during pottery firing. As Wedgwood discovered, clay blocks shrank in a kiln based on temperature. The higher the heat, the more shrinkage there was. For this innovation, he was elected a member of the Royal Society in 1783. As a wealthy entrepreneur of the 18th century, Wedgwood created goods that met the demands of the consumer revolution and fueled Britain's Industrial Revolution.

Josiah Wedgewood


As a general rule, pyrometers measure the temperature of a body by measuring the radiation it emits. The advantage of radiation devices is that they do not require touching the material being measured.


The pyrometer can be classified into mainly two types based on it’s working principle,

*Optical Pyrometer

*Infrared/Radiation Pyrometer

Optical pyrometers – These devices measure thermal radiation in the visible spectrum. Their measurements are based on the color of the visible light emitted by extremely hot objects. Visual comparisons can be performed between a calibrated light source and the targeted surface. As the temperature of the filament and the target match, their thermal radiation intensity will also match, resulting in the filament becoming almost invisible while merging into the targeted surface in the background. By doing so, a temperature reading can be obtained from the current that passes through the filament.

Infrared / radiation pyrometers – These devices measure the temperature of an object based on its radiation output. They can handle thermal radiation in the infrared region, usually 2 ~ 14 µm (80 ~ 550 µin). When a thermocouple is partially heated, it can produce an electric current. The thermocouple will then generate a higher current according to the heat emitted. Using the current, a dial displays the temperature. These pyrometers are made from pyroelectric materials such as polyvinylidene fluoride (PVDF), triglisine sulfate (TGS), and lithium tantalate (LiTaO3).


The pyrometer is best suited to measuring moving objects or surfaces that cannot be reached or touched, such as:

Blast Furnace temperature measurement, Smelter Industry, Metallurgical Furnace operation, Steam Boiler, Gas Turbine Engines, Hot Air Balloon, Medical Industry, Induction Heat Treating, Crystal Growth, Glass Manufacture, Gas Turbine Engines and to measure the temperature of liquid metals and highly heated materials.


Here at MurCal we carry a variety of pyrometers by the leader in the field, Hewitt Instruments. As the story goes, in 1952 while in the trucking business, John T. Hewitt designed and developed the first pyrometer (E.G.T) used for trucks. In 1955 Hewitt Industries was formed and began developing the market for users and O.E.M.’s around the world. Hewitt maintains this leadership through the highest quality in design and product reliability.

Shop our selection here: Hewitt Pyrometers | MurCal

We also carry a handful of exhaust pyrometers by our partner Murphy by Enovation, available here: Exhaust Pyrometers | MurCal and an unique configurable temperature scanner/pyrometer with a built-in power supply by FW Murphy: TDXM-DC (10702748): Temperature Scanner / Pyrometer (

It all comes down to wavelength and it depends on what is the target material, the distance to and the size of the target, what is the temperature range needed, if there are any optical obstructions, and what is the method of heating.

But you don’t need to figure it out by yourself, give us a call today!! 

Contact Us with Questions!


Phone: 661-272-4700

Email: sales@MurCal.Com

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