The pyrometer is an instrument created to measure heat , based on the level of radiation that certain hot objects emanate.


What is a pyrometer?

The pyrometer is an instrument, other than the thermometer, designed to estimate high-level temperatures , typically above 600 degrees Celsius . The pyrometer sets its caloric estimation range from minus 50 degrees Celsius to 4000 degrees Celsius. You can calculate the temperature of an object without sustaining contact with it.

  • Definition
  • Pyrometer Features
  • History
  • Who invented it
  • What is a pyrometer for?
  • Types
  • Parts of a pyrometer
  • How a pyrometer works
  • How to use a pyrometer
  • How it differs from the thermometer
  • Importance


Measuring heat has always been a problem for those who work in mechanics. This is due to the wide need that man has had for fire , and in turn, the danger that this has represented for himself. It is no secret to anyone that the thermometer is quite a useful instrument for this purpose, although like any other, it has significant limitations.


It could be said that, among the main difficulties found in relation to the measurement of heat, is the closeness that we assume with it. No human being (and very few of his instruments) survive the caloric densities of some objects, and to avoid the fate of Icaro , other instruments had to be developed.

One of the instruments that technology has left us has been the pyrometer . This is nothing more than an instrument to measure high levels of heat . It is based on the measurement of the radiation emissions released by some hot objects. It is an instrument whose measuring range goes from 50 degrees below zero to 4000 degrees Celsius . It should also be noted that unlike other instruments, it does not depend on contact with a material to measure its temperatures.

Let’s see, now, some of its characteristics.

Pyrometer Features

It is an instrument capable of capturing temperatures without coming into contact with the object. This is very advantageous, due to the difficulty of some objects to be measured. For example, the very high temperatures of the same, or the inaccessibility that it presents.

It features a high level of metric precision. This is due to the internal devices that help to accurately calculate the temperature, and not to let external elements disturb the reading.

It has a wide measurement spectrum. As already said, this can go from 50 degrees below zero , up to 4000 degrees Celsius . It is beyond the reach of many other instruments.

Wide response speed. Its reading capacity, which is electronic, is short. It doesn’t take a long time to come up with your estimates.


Originally, the pyrometer was used to estimate the expansion of some ferrous objects when subjected to very high temperatures. It should be noted that it was also used to measure the heat of the ovens. This was a capacity that the instruments of the time, sadly, did not possess. Over the years, its use was restricted to teaching caloric events for students of chord careers. This situation, fortunately, changed over time. Currently the instrument uses electronic means for its application.

Who invented it

On this point there is a certain gloom. It is said that, originally, there were two inventors. These were Pieter van Musschenbroek and Josiah Wedgwood . Both had the opportunity to invent very similar instruments and with the same purposes, each one for his own part. However, it must be clarified that the current pyrometers have little to do with the old instruments.

What is a pyrometer for?

The usefulness of the pyrometer is in the capabilities that other instruments of its type do not have. You can measure objects from a distance, without coming into contact, such as vapors or ovens. In the same way, and thanks to their wide range, they can measure very, very high temperatures, above 600 degrees Celsius.


Among the most used pyrometers, we could name:

Radiation pyrometer

This pyrometer is based on radioactive emissions. Through radiation, internal mechanisms carry out translation processes that allow the identification of temperature levels.

Optical pyrometer

This type of instrument captures the radiation observable through the human eye. The bandwidth of this is used to estimate the degree of temperature here.

Infrared pyrometer

Very similar to the first of the aforementioned pyrometers, with the exception that its measuring range, on this occasion, is much greater.

Parts of a pyrometer

Among some of the parts of the pyrometer that we could highlight, we have the following:

  • An optical capture system that can perceive radiation or energy emissions from some source.
  • A device capable of transforming that energy into data that can be interpreted by the system.
  • An adjustment system in charge of calibrating emissions . This implies that the system can compare the readings given with its external source.
  • A compensation system that allows to purify the reading of the disturbances of the external world . This implies that the reading will not be contaminated by the temperatures that are suffered by the environment.

How a pyrometer works

It is a system based on Stefan Boltzmann’s law. This establishes that the amount of energy emitted by an object is directly proportional to the temperature of an object. This means that the temperature of an object will be evaluated based on the energy emitted by it.

How to use a pyrometer

Its use, or at least the use that we can give to modern pyrometers , is quite simple. Although it depends on the type of pyrometer that we have at hand, the instrument is placed in front of the heat-emitting object. Then, it captures the energy emitted by it, and the calibration systems are in charge of translating this energy into caloric terms . The result ends up being a temperature reading in degrees Celsius.

How it differs from the thermometer

Among the differences that we can highlight, we have:

  • The thermometer requires contact with the object to measure heat. The pyrometer, no.
  • The pyrometer has a greater estimation range than the thermometer.
  • The pyrometer uses radiation to estimate temperature. The thermometer measures the latter directly.


It is a very useful instrument to measure degrees and sources of temperature to which conventional instruments do not have access. It facilitates the work of mechanics who work with heat, to the point that they do not have to have direct access to it, or risk their integrity in this regard.

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