Infrared (IR) heat sensors work by detecting and measuring infrared radiation emitted by objects, which is directly related to their temperature.
Here's a breakdown of the process:
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Emission of Infrared Radiation: All objects above absolute zero (0 Kelvin or -273.15°C) emit infrared radiation. The hotter an object, the more infrared radiation it emits. This radiation is part of the electromagnetic spectrum but is invisible to the human eye.
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Focusing the Infrared Radiation: An infrared sensor, like that found in an IR thermometer, uses a lens to focus the incoming infrared radiation onto a detector. This lens is typically made of materials like germanium or silicon, which are transparent to infrared light. The focusing concentrates the energy for more accurate measurement.
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Detection with a Thermopile (or other Detector): The core of the sensor is the detector. One common type is a thermopile. A thermopile consists of multiple thermocouples connected in series.
- Thermocouples: A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature.
- How the Thermopile Works: When infrared radiation strikes the thermopile, it heats the "hot" junctions of the thermocouples. The "cold" junctions are kept at a reference temperature. The temperature difference between the hot and cold junctions generates a voltage.
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Signal Processing: The voltage produced by the thermopile (or other detector type) is very small. It is amplified and processed by electronic circuitry within the sensor.
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Temperature Calculation: The processed signal is then used to calculate the temperature of the object. The sensor's internal circuitry uses a calibration curve to relate the voltage to a specific temperature. This calibration curve is based on the Stefan-Boltzmann law, which describes the relationship between an object's temperature and the amount of radiation it emits. Factors like emissivity (the object's ability to emit infrared radiation) are also taken into account.
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Display of Temperature: Finally, the calculated temperature is displayed on a screen, allowing the user to read the object's temperature without physical contact.
In summary, infrared heat sensors act as light funnels, but instead of visible light, they gather and measure infrared radiation to accurately determine the temperature of an object.
