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Technical principle of infrared forehead thermometer

Source: Time:2020-08-16 23:31:08 views:

All objects with a temperature higher than zero degrees (-273.15°C) are constantly emitting infrared energy into the surrounding space. Its radiation characteristics, radiation energy size, wavelength distribution, etc. are closely related to the surface temperature of the object. Conversely, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined, which is the mechanism of infrared radiation temperature measurement.

The human body, like other living organisms, radiates infrared energy to the surroundings. Its wavelength is generally 9-13μm, which is in the near-infrared band of 0.76-100μm. Since the light in this wavelength range is not absorbed by the air, that is to say, the amount of infrared radiation radiated by the human body has nothing to do with the environmental impact, but is related to the amount of energy contained and released by the human body. Therefore, as long as the infrared energy is radiated to the human body The measurement can accurately determine the surface temperature of the human body. The human body infrared temperature sensor is designed and manufactured according to this principle.

Infrared temperature sensor

At present, the infrared temperature sensors on the market mainly have the following types according to the materials used for energy conversion:

(1) Pyroelectric type: triglyceride sulfate, lithium tantalate, etc.

(2) Thermopile type: N-type and P-type polysilicon

(3) Diode type: single crystal or polycrystalline PN junction

(4) Thermal capacitance type: bi-material film

(5) Thermistor type: vanadium oxide, amorphous silicon, etc. In fact, these types are only different in conversion methods and material energy efficiency ratios after receiving infrared energy.

forehead thermometer

forehead thermometer

forehead thermometer

forehead thermometer

forehead thermometer

forehead thermometer


At present, the infrared sensors used in ear and forehead thermometers are thermopile type, and the basic physical principle is the Seebeck effect.

Parameters of thermopile temperature sensor:

Measuring range: -50℃-100℃;

Measurement accuracy: within 0.1℃, within ±0.1%;

Working temperature: -20℃-+85℃;

Maximum measuring distance: ≦0-50mm (with lens 300-500mm)

Output voltage: 0-10mV;

The maximum range of thermopile temperature sensor can be -60℃ to +1200℃

There are two main packaging forms for the finished product drawing of infrared thermopile sensor: TO46(TO18)/TO39(TO5)

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