A pyrometer is a non-contact device that measures temperature by detecting infrared (IR) radiation emitted by hot objects and converting it into a temperature reading in Celsius (°C) or Fahrenheit (°F). They are often used in industrial applications to measure the temperature of objects that are too hot to touch, such as molten metal or objects heated in furnaces.
Pyrometers detect infrared radiation emitted by objects and use this data to calculate their temperature without making contact. They are highly accurate and can directly measure the temperature of all types of materials and gases over a wide temperature range.
Pyrometers are essential in industries requiring precise, non-contact temperature measurement, such as metalworking, glassmaking, and food processing, where accurate thermal control optimises production quality.
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What Does a Pyrometer Measure?
A pyrometer measures the amount of IR radiation emitted by an object. IR radiation is a type of electromagnetic radiation that is not visible to the human eye but can be detected by specialised optics and detectors contained within the pyrometer. When an object is heated, it emits IR radiation, and the amount of radiation emitted is directly proportional to the object’s temperature. A pyrometer converts this radiation into an electrical signal and the output is given in either Celsius (°C), Kelvin (K) or Fahrenheit (°F) temperature scale.
What Are the Advantages of a Pyrometer?
One of the main advantages of a non-contact pyrometer over a contact thermometer is that it does not need to make physical contact with the object being measured. This makes it suitable for measuring aggressive materials including very hot or chemically aggressive materials that would damage other types of sensors. Non-contact pyrometers also have a very fast response time and can measure moving objects without interference.
Additionally, a non-contact pyrometer does not affect the temperature of the object, unlike a contact thermometer, which draws heat from the object by thermal conduction and changes its temperature. This makes a pyrometer ideal for measuring objects that are moving, have a rapidly changing temperature profile or will be influenced or damaged by using a contact sensor.
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What Are the Different Types of Pyrometers?
There are broadly four main types of pyrometers. Within each type, there is a wide variety of models optimised to make them best suited for certain applications.
- A single-colour pyrometer only measures one wavelength. These can be supplied in specific wavelengths to suit the object and the temperature range of the object that is being measured, for example, a wavelength of 4.8…5.2µm is used for measuring the surface temperature of glass. When selected correctly for given applications, they will provide the very best measurement accuracy.
- A dual-colour pyrometer (or ratio pyrometer) consists of two single-colour pyrometers in the same housing, with both detectors operating on different wavelengths but measuring the same target and using the ratio to determine the temperature.
A dual-colour pyrometer is not affected by contaminants between the pyrometer and the object such as steam, smoke, dust or contaminants on the pyrometer optics. They are also suitable for measuring objects that are smaller in size than the measurement spot and they are less sensitive to emissivity changes.
- A fibre optic pyrometer transmits the radiation from the optical head via an optical fibre to the measuring transducer, which includes the detector and all processing electronics. The advantage of this is that the electronics are kept away from extreme heat, making the devices suitable for harsh environments or areas with high electromagnetic radiation.
- Transfer standard pyrometers have extremely high accuracy specifications and are used for verification to transfer temperature data from a primary infrared source to other calibration sources. They have a resolution of 0.01°C with extreme accuracy and long-term stability and are provided with traceable calibration certificates.
What Are Pyrometers Used For?
Pyrometers are commonly used to measure the temperatures of hot surfaces or objects in production and manufacturing processes. They are also an ideal solution for measuring the temperatures of hard-to-reach or moving objects and are particularly well-suited for use in extreme working conditions due to their durability and accuracy.
Pyrometers can be used in many different industries such as metallurgy, glassmaking and ceramic production, automotive manufacturing, food processing and research laboratories.
What Is Emissivity?
Emissivity is a measure of the ability of a surface to emit thermal radiation. It is defined as the ratio of the thermal radiation emitted by a surface to the thermal radiation emitted by a blackbody at the same temperature. In other words, it is a measure of how efficiently a surface radiates heat. The ratio varies from 0 to 1, or from 0% to 100%.
Different materials will have different emissivity. It is important to set the pyrometer emissivity to match the material that is being measured. Emissivity refers to a material’s ability to emit infrared radiation, and it can vary depending on the material and the measurement wavelength. This affects the accuracy of temperature readings. It is important to always measure in the wavelength where the emissivity is the highest for that material.
Learn More about Pyrometers
In summary, pyrometers are an accurate tool for non-contact temperature measurement. Pyrometers work by measuring IR and are useful in various industries and working conditions. Learn more about pyrometers by using the links below:
- Learn more about how pyrometers work
- Learn more about the advantages of pyrometers compared to contact thermometers
- Learn more about the different types of pyrometers
- Learn more about what information you need to select the correct pyrometer
- Learn more about spot size when selecting a pyrometer
Visit our temperature measurement and thermal processing page to learn more about temperature measurement products at Control Metrix, including pyrometers. To speak to a product specialist to find out how a pyrometer could benefit your company, call +44 (0)1823 761 309.
