For a long time, agricultural soil testing and fertilization have relied on conventional photoelectric colorimeters, which require soil samples to be retrieved from the field, dried, and then sent to the laboratory for measurement. There are many shortcomings in this method, such as large investment in instruments, inability to be portable, many auxiliary pieces of equipment, and high testing costs, which seriously restrict the implementation of scientific and rational fertilization in grass-roots rural areas. The portable soil nutrient photoelectric colorimeter is developed to meet the needs of agricultural production practice, in addition to the conventional photoelectric colorimeter.
In addition, according to the needs of rapid soil measurement, the measurement of temperature and other parameters should be completed online and temperature correction should be carried out. If conditions permit, a guiding fertilization system should be embedded in the photoelectric colorimeter so that the user can directly apply the soil test after soil measurement. Data should be used to guide fertilization. The pocket colorimeter uses LCD characters to display the measurement steps, avoiding the shortcomings of LED displays that consume a lot of power and cannot be seen clearly in strong sunlight. It supports micro-printers and supports both AC and battery power supplies. The instrument is small in size, light in weight, and easy to maintain, making it very suitable for field operations.
According to the Lambert-Beer law, the light intensity through the solution can be reflected by the photocurrent, so the photocurrent sensor can be selected, and then the voltage signal is obtained through the current-voltage converter and sent to the CPU for processing. Another method is to choose a voltage sensor that has integrated an operational amplifier, such as the Pocket Colorimeter produced by ATO Colorimeter.org, which is developed with the development of microelectronics technology and has the advantages of low price, good performance. It has the advantages of high integration and good interchangeability.
The portable soil nutrient photoelectric colorimeter fully takes into account the actual needs of agricultural production, focusing on portability, low cost and high stability. The light source constant power technology and the light intensity automatic adjustment technology are adopted, so that the light intensity can be automatically adjusted to the best state according to different wavelengths, and the absorbance linear automatic correction technology is adopted to correct the error caused by the non-monochromaticity of the light so that the portable The test linearity of the photoelectric colorimeter reaches the linear effect of the caliber 8mm portable colorimeter; the temperature correction model is embedded in the instrument, and the temperature range can reach -20 ~ 40 °C, which reduces the linear error value by half; improves the intelligence level of the instrument. The overall size is 205 mm × 70 mm × 100 mm, the weight is 500 g, and the price is low, which is very suitable for rural grassroots units.
