In the study of plant physiology, the determination of plant photosynthesis is one of the important research work. It is generally measured by measuring the value of illuminance and photosynthetically active radiation, and the measurement of illuminance and photosynthetically active radiation requires a light sensor and photosynthetically active radiation sensor.
To understand the difference between the two sensors, we need to start with illuminance and photosynthetically active radiation.
Illuminance, referred to as illuminance, generally refers to the surface density of the luminous flux on the surface of the plant by light, that is, the luminous flux per unit area. So illuminance is a measure of how illuminated a surface is, in Lux. It is based on the perception of the human eye. Due to the different sensitivity of human eyes to different wavelengths of light, the same light quantum flux density of 1000μE/m2 / s, the sensitive green light lux will be larger, while the less sensitive red light Lux will be smaller. Under certain conditions, when the light intensity increases, the intensity of photosynthesis will also increase, but when the light intensity exceeds the limit, the stomata on the leaf surface of the plant will close, and the intensity of photosynthesis will decrease. Therefore, the use of illumination sensor to control the illumination has become an important factor affecting crop yield.
Photosynthetically active radiation is an important environmental factor in plant growth. In facility agriculture or horticultural research, the optimum light intensity and duration should be determined according to the plant species and its growth stage. For example, plants generally need more and more intense light during the vegetative and reproductive stages of growth than during seed setting and harvest. Therefore, in facility agriculture or horticulture, reasonable regulation of photosynthetically active radiation can not only effectively save light and electricity, but also promote the increase of yield.
Since photosynthetically active radiation is mainly tested in the wavelength range of 400 nm to 700nm, different spectral modes of lamps will affect the relationship between light intensity and photosynthetically active radiation. So their rough relationship is: 1000 lux = ~ 19.53 μE/m2 / s PAR (1μE/m2 / s PAR = ~ 50 lux).
Knowing the relationship between illumination and photosynthetically active radiation, we can easily see the difference between illumination sensor and photosynthetically radiation sensor.
One, The output numerical units of measurement are different
Illuminance sensor can convert illuminance size into electrical signal, the output numerical unit of measurement is LUX. The photosynthetically active radiation sensor adopts photoelectric induction principle, and the output value is measured in units of 0 ~ 2500μmol/m2 ·s.
Two, the measurement range is different
The measurement range of luminance sensor is 0 ~ 60000 LUX or 0 ~ 200000 LUX. And photosynthetically active radiation refers to the wavelength range of 400 ~ 700 nm for photosynthesis of vegetation that part of the solar radiation, photosynthetically active radiation sensor measurement range of 0 ~ 2500μmol/m2 ·s.
Three, applicable to different scenarios
Photosynthetically active radiation sensor can only measure the effective radiation amount of plants during photosynthesis, and the illuminance sensor can be used in agricultural occasions, but also for electronic equipment production line and other occasions requiring illumination measurement.