A basic infrared temperature sensor, also known as an infrared thermometer or pyrometer, measures the surface temperature of an object without making physical contact. It does this by detecting and analyzing the infrared radiation emitted by the object.
Here's how it works:
Infrared Emission: All objects with a temperature above absolute zero (-273.15°C or 0 Kelvin) emit infrared radiation. The amount and wavelength of this radiation depend on the object's temperature. Hotter objects emit more intense radiation with shorter wavelengths.
Optics: The infrared temperature sensor has an optical system that collects and focuses the infrared radiation from the object onto a sensor. The optical system can be a lens or a combination of mirrors and lenses, depending on the design of the sensor.
Infrared Sensor: The sensor used in these thermometers is typically a thermopile or a microelectromechanical system (MEMS) that responds to infrared radiation. The thermopile is composed of several thermocouples connected in series, and each thermocouple generates a voltage proportional to the temperature difference between its hot and cold junctions.
Temperature Calculation: The infrared radiation from the object heats up the thermopile, causing a temperature difference between its junctions. This temperature difference generates a small voltage output, which is proportional to the object's surface temperature. The sensor then converts this voltage into a digital signal.
Calibration: The sensor needs to be calibrated to ensure accurate temperature measurements. Calibration involves determining the relationship between the sensor's voltage output and the corresponding temperature. Manufacturers perform this calibration during the sensor's production, and some infrared thermometers allow for user calibration.
Display: The sensor's digital signal is then processed and displayed as a temperature reading on the thermometer's screen. Some devices may also have additional features like emissivity adjustment, which allows users to compensate for the varying emissivity of different materials.
It's important to note that infrared thermometers are most accurate when measuring the temperature of a target that is larger than the sensor's spot size. Smaller spot sizes can lead to partial coverage of the object, which might result in inaccurate readings due to variations in temperature across the object's surface. Additionally, these thermometers are suitable for measuring non-reflective and opaque surfaces but may not work accurately with reflective or transparent materials.