Glossary for Infrared Temperature Sensors

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Infrared Temperature Sensor

An infrared temperature sensor detects the infrared emission energy emitted from the surface of the measurement target, and converts it into a temperature signal for output.
This is why the sensor can measure the surface temperature without contact with the target object.

Heat Emission

There are three types of heat transmission: heat conduction, heat transfer (convection), and heat emission (radiation).
Heat conduction: heat is transferred through objects.
Heat transfer: heat is transferred by the air or liquid flow. Also referred to as convective heat transfer.
Heat emission: heat is transferred by the far-infrared radiation.

Far-infrared Radiation

The wavelength of infrared ray ranges from 0.7 μm to 1 mm, in which the range of 0.7 to 2.5μm is known as near-infrared , the range of 2.5 to 4μm is called mid-infrared, and 4μm to 1 mm is far-infrared .
Infrared ray temperature sensors that use the atmospheric window, are almost free from absorption due to the presence of the atmosphere.

Thermopile

Detection elements are roughly divided into two types: thermal and quantum types. Our sensors are of the thermal type and utilize thermopiles to sample infrared radiation.
Thermopiles are multiple thermocouples connected together in series, utilizing the Seebeck effect, in which the thermal electromotive force occurs according to the thermal temperature gap between the hot junction and cold junction contacts.

FOV（Field of View）

The viewing angle for the sensor is referred to as the FOV (Field of View).
Usually the sensor’s FOV is the angle which can obtain 50% of the maximum sensitivity.

Emission rate

Some important laws in heat emission (such as Planck's law of radiation, Wien's displacement law, and the Stefan-Boltzmann law) are based on the condition where all of the emission energy of the object can be entirely (100%) emitted.
The emission energy of the target measured in actual cases is less than that of a perfect black body. The ratio of energy emitted when compared to that of black body radiator is called the emissivity.

4 to 20 mA output

A form of analog signal for industrial uses
This is a type which is more focused on anti-noise performance rather than voltage output.
The minimum value is 4mA, which enables detection of disconnection (which would be 0mA).
By inserting a shunt resistance of 250Ω(1/4 or more), current can be converted to voltage, where the conversion to a 1V to 5 V signal is possible.

1 to 5 V output

A type of analog signal for industrial use, just like 4-20 mA.
Minimum value is 1 V, and disconnection (which would be 0 V) can be detected.