Operating principal of Infrared Sensor
What is Infrared light？
Infrared is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves.
Black-body radiation
All normal matter emits electromagnetic radiation when it has a temperature above absolute zero. A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The radiation emitted by a black body in thermal equilibrium with its environment is called as black -body radiation. Black-body radiation has a characteristic, continuous frequency spectrum that depends only on the body's temperature,called the Planck spectrum or Planck's law like below.
Energy(All the energy emitted from black-body) integrated the spectral radiance through all the wavelength range is highly dependent on temperature and will be proportional to the 4th power of temperature. This relation was named as Stefan–Boltzmann’s law.
Emissivity
The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation that most commonly includes both visible radiation (light) and infrared radiation, which is not visible to human eyes. Emissivity of specular body is 「０」and emissivity of perfect black body is「1」.
Emissivity of all the material will be from 0 to 1.
What is Thermopile(Thermocouple)？
A thermopile is an electronic device that converts thermal energy into electrical energy. It is composed of several thermocouples connected usually in series or, less commonly, in parallel. It can not measure absolute temperature but generate an output voltage proportional to a local temperature difference or temperature gradient. Such a device works on the principle of the thermoelectric effect, i.e., generating a voltage when its dissimilar metals (thermocouples) are exposed to a temperature difference. Energy of infrared light radiated from a measurement object will be absorbed by heat absorption membrane and thermopile under the heat absorption membrane will produce a temperature dependent voltage. This phenomenon will be called as Seebeck effect. Thermoelectromotive force and reference temperature can be translated into the temperature of measurement object.
What is Seebeck effect?
The Seebeck effect is the electromotive force (EMF) that develops across two points of an electrically conducting material when there is a temperature difference between them.The EMF is called as Seebeck EMF (or thermo/thermal/thermoelectric EMF). The ratio between the EMF and temperature difference is the Seebeck coefficient. The Seebeck effect is a classic example of an electromotive force (EMF) and leads to measurable currents or voltages in the same way as any other EMF. This EMF will only depend on 2 conducting materials and temperature difference(ΔT) between 2 end points of conducting materials.
What can be done by "Infrared Sensor"？
Multiple persons can be detected through infrared sensor(8 x 8 pixels) installed on the ceiling. Also it is possible to measure the temperature.
Example of Infrared Sensor application
Application
example 1. Microwave oven
- Temperature distribution will be measured by infrared sensor module with 8x8 pixels
- Surface temperature of food will be measured to determine operation mode of automatic cooking or warming function
To determine heating time and heating temperature etc.
example 2. Range food
- Temperature of cooking stove surface will be monitored by infrared sensor module with 8x8 pixels
- Ventilation air volume will be adjusted automatically based on measured temperature
example 3. Building management system(BEMS)
- Multiple bit configuration infrared sensors such as 8X8 pixels will be installed on the ceiling.
- Positions of persons or movement will be detected and can be fed back to the building management system such as Illumination or air conditioning control.
Can detect even in darkness
Human presence can be detected
Operation will be determined by detecting people and temperature
