A radiation thermometer, commonly known as a pyrometer, is a non-contact temperature measurement device that operates based on the principle of detecting the infrared radiation emitted by an object. Here are the basics of how a pyrometer works:

1. Principle of Infrared Radiation:

   • All objects with a temperature above absolute zero (-273.15°C or 0 Kelvin) emit electromagnetic radiation in the form of infrared radiation. The intensity and wavelength distribution of this radiation depend on the temperature and emissivity of the object.

2. Detection of Infrared Radiation:

   • A pyrometer uses optics to focus the infrared radiation emitted by the target object onto a detector element, typically a thermopile or a photodiode.

3. Temperature Calculation:

   • The detector element converts the incoming infrared radiation into an electrical signal, which is then processed by the pyrometer's electronics.
   • The pyrometer's electronics analyze the intensity of the detected radiation and use it to calculate the temperature of the object based on the Stefan-Boltzmann law or Planck's radiation law.
   • The temperature reading is typically displayed on a digital screen or analog gauge.

4. Emissivity Correction:

   • Emissivity is the ratio of the infrared radiation emitted by an object to that emitted by a perfect blackbody at the same temperature. Since most real-world surfaces do not behave as perfect blackbodies, pyrometers often include a feature to adjust for the object's emissivity to ensure accurate temperature measurements.

5. Types of Pyrometers:

   • Pyrometers can be classified into two main types: single-wavelength and multi-wavelength.
     • Single-wavelength pyrometers operate at a specific infrared wavelength and are suitable for measuring the temperature of objects with known or relatively constant emissivity.
     • Multi-wavelength pyrometers use multiple infrared wavelengths to compensate for variations in emissivity and are suitable for measuring the temperature of objects with changing emissivity or unknown emissivity.

6. Applications:

   • Pyrometers are used in various industrial and scientific applications, including metallurgy, glass manufacturing, ceramics, automotive, aerospace, and research laboratories.
   • They are particularly useful for measuring the temperature of objects that are moving, inaccessible, or at extremely high temperatures, where contact-based temperature measurement methods may be impractical or unsafe.

Overall, pyrometers are versatile instruments for non-contact temperature measurement, offering accuracy, speed, and convenience in a wide range of applications.