The chlorophyll detector is simply referred to as a chlorophyll content meter or chlorophyll measuring instrument, which is an instrument that displays the greenness of plants by measuring the spad value. The SPAD502 chlorophyll content meter is the highest-end instrument in the chlorophyll measuring instrument. It measures the SPAD value to guide the application amount of nitrogen fertilizer and understand the growth status of the plant.
The chlorophyll detector is based on the absorption of the chloroplast pigment extract in the visible spectrum, using a spectrophotometer to measure its absorbance at a specific wavelength, and the content of each pigment in the extract can be calculated using a formula. According to Lambert-Beer's law, the absorbance A of a colored solution is proportional to the solute concentration C and the thickness L of the liquid layer, that is, A = αCL where: α ratio constant.
Set the instrument
Chlorophyll detector is abbreviated as chlorophyll content meter or chlorophyll measuring instrument, which is an instrument that displays the greenness of plants by measuring the spad value. The SPAD502 chlorophyll content meter is the highest-end instrument in the chlorophyll measuring instrument. It measures the SPAD value and guides the amount of nitrogen fertilizer applied while understanding the growth status of the plant.
principle
The chlorophyll detector is based on the absorption of the chloroplast pigment extract in the visible spectrum, using a spectrophotometer to measure its absorbance at a specific wavelength, and then the formula can be used to calculate the content of each pigment in the extract. According to Lambert-Beer law, the absorbance A of a colored solution is proportional to the solute concentration C and the thickness L of the liquid layer, that is, A = αCL where: α proportional constant. When the concentration of the solution is in percent concentration and the thickness of the liquid layer is 1 cm, α is the absorption coefficient of the substance. The absorption coefficients of various colored substance solutions at different wavelengths can be obtained by measuring the absorbance of pure substances of known concentrations at different wavelengths. If there are several kinds of light-absorbing substances in the solution, the total absorbance of this mixture at a certain wavelength is equal to the sum of the absorbances of the components at the corresponding wavelengths. This is the sum of absorbance. To determine the content of chlorophyll a, b and carotenoids in the mixed extract of chloroplast pigments, just determine the absorbance A of the extract at three specific wavelengths, and according to the chlorophyll a, b and carotenoids at this wavelength The absorption coefficient can be obtained to determine its concentration. In order to eliminate the interference of carotenoids when measuring chlorophyll a and b, the wavelength of the monochromatic light used is to select the maximum absorption peak of chlorophyll in the red light region.
use
The chlorophyll detector can instantly measure the relative chlorophyll content or "greenness" of the plant. The chlorophyll content in the plant leaves indicates the condition of the plant itself. The leaves of plants with good growth will contain more chlorophyll. The chlorophyll content and the nitrogen in the leaves The content of chlorophyll has a very close relationship, so the chlorophyll measurement value can also indicate the true nitro demand of the plant. This portable chlorophyll analyzer can guide the rational application of nitrogen fertilizer, improve the utilization rate of nitrogen, and protect the environment (prevent excessive application) More nitrogen fertilizers will pollute the environment, especially water sources).
Working principle of chlorophyll meter
Two LED light sources emit two kinds of light, one is red light (peak wavelength 650nm), one is infrared light (940nm), two kinds of light penetrate the blade and hit the receiver, the optical signal is converted into analog signal, analog signal It is amplified by the amplifier and converted into a digital signal by an analog / digital converter. The digital signal is processed by the microprocessor, and the SPAD value is calculated and displayed on the LCD screen.
Calibration and calculation of measured value of chlorophyll meter
(1) During the calibration process, the indenter does not clamp the sample, the two LEDs emit light in sequence, the received light is converted into an electrical signal, and the ratio of light intensity is used to calculate.
(2) After the sample is clamped by the indenter, the two LEDs emit light again, the light transmitted through the blade hits the receiver, is converted into an electrical signal, and the intensity ratio of the transmitted light is calculated.
(3) The values ​​of steps 1 and 2 are used to calculate the SPAD measurement value, that is, the current relative chlorophyll content of the sample leaf clamped
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