What is an infrared temperature sensor?
Non-contact infrared temperature sensor generally uses pyroelectric or photoelectric detectors as detection elements.
It can realize the temperature measurement of a large area, and can also measure the temperature of a certain point on the measured object. Can be portable or stationary. It does not touch the measured object during temperature measurement, and the temperature will not be affected by the state of the measured object.
Types of Infrared Temperature Sensors
The infrared temperature sensor has two categories according to the measurement principle: photoelectric infrared temperature sensors and pyroelectric infrared temperature sensors. Pyroelectric infrared temperature sensor uses the thermal effect of infrared radiation to measure the absorbed infrared radiation through thermoelectric effect, pyroelectric effect and thermistor. Indirectly measure the temperature of objects radiating infrared light.
The principle of infrared temperature sensor
The infrared temperature sensor working principle is the law of black body radiation. All objects above absolute zero in nature are constantly radiating energy outward, and the magnitude of the radiated energy of an object is related to its surface temperature. The higher the temperature, the stronger the infrared radiation it emits.
（Blackbody spectral radiance plot at different temperatures）
We can see from the curve in the figure:
- At any temperature, the spectral radiance of a black body varies continuously with wavelength, and each curve has only one maximum value.
- As the temperature increases, the wavelength of the corresponding spectral radiation maxima decreases. This shows that the proportion of shortwave radiation in blackbody radiation increases with temperature.
- With the increase of temperature, the black body radiation curve increases overall. Spectral radiance is also greater at higher temperatures at a given wavelength.
The infrared temperature sensor types: Measure the thermal radiation of an object at its full wavelength to determine the radiation temperature of the object (full radiation thermometry).
Measure the monochromatic radiance at a specific wavelength and calculate its brightness temperature (brightness thermometry).
Change the ratio of the monochromatic emissivity of the object at the two wavelengths to the temperature to obtain temperature data (colorimetric thermometry).
The luminance thermometry method does not require ambient temperature compensation, and the emissivity error is small. However, it works in the short wave region and is only suitable for high-temperature measurement.
Part of the optical system for colorimetric temperature measurement is blocked to reduce the influence of smoke and dust. Select the appropriate band, the emissivity difference between the bands is small.
Infrared temperature sensor use
When measuring, first aim at the measuring object, and then press the trigger to read the data on the LCD screen of the instrument. Pay attention to adjust the ratio of distance and spot size. There are some important things to remember when using infrared temperature sensors:
Infrared temperature sensors can only measure surface temperature, not internal temperature. Glass cannot measure temperature, glass has very special reflection and transmission properties. However, it is possible to measure temperature with an infrared window.
Infrared sensors do not measure the temperature of bright or polished metal surfaces (stainless steel, aluminum, etc.). Locate the hot spot, find the hot spot, and aim the instrument at the target. The target is then scanned up and down until a hot spot is identified. Pay attention to ambient conditions: steam, dust, smoke, etc.
Smooth surfaces can block the optics of the instrument and prevent accurate temperature measurements. Ambient temperature, if the thermometer is suddenly exposed to an ambient temperature difference of more than 20 degrees, allow the instrument to adjust to the new ambient temperature within 20 minutes.
