Research Of Portable, Near-infrared Spectrometer Circuit System For Rapid Soil Nutrients Analysis

This paper describes the designs of detector drive system and data acquisitionsystem, which are crucial parts of portable, near-infrared spectrometer for rapid soilnutrients analysis.Portable, near-infrared spectrometer for rapid soil nutrients analysis is the keyequipment to predict soil nutrients, and it is the tool to achieve precision agriculture.Precision agriculture needs to put agricultural production process under control. Oneof the most important aspects is to fertilize in precisely. It is significant to obtain thesoil nutrients information which needs a large number of portable, rapid instruments.Near-infrared spectroscopy is simple, rapid, and no need reagents. This analysismethod is well suited for the detection of soil nutrients. It is important to makeportable, near-infrared spectrometer for rapid soil nutrients analysis, to meet theneeds of testing of soil nutrients.In this paper, studies on circuit system of a kind of near-infrared spectrometerfor rapid soil nutrients analysis are introduced. The designs of detector drivingcircuit system and data acquisition system are given. Tests and experiments with thespectrometer are also introduced. The following is the main contents of this paper:The first part involves the importance of near-infrared spectrometer for rapid soil nutrients analysis, and some key concepts. In the beginning backgrounds of thispaper are introduced. Then, fundamental physical principles of near-infraredspectroscopy are explained, also including the principles of chemometrics methods.In the end, the structures of various portable near-infrared spectrometers areintroduced, and their advantages and disadvantages are summarized. Research anddevelopment status of this kind of equipment are briefly summarized.The second part is about the structure of the spectrometer. Using immovablegrating and linear array detector, the optical systems is compact and stable. Lightsource is tungsten halogen lamp, and samples are detected by fiber probe.The third section describes the design of detector driving system. Complexprogrammable logic device provides driving signal. The detector also need stablevoltage references and temperature control circuit. The output signal of detectorshould be amplified and DC-offset should be eliminated.The next section describes the design of data acquisition system. Dataacquisition is completed by a16bit analog-digital conversion chip. The dataacquired is processed and transmitted by control system based on STM32. Thedesign of power supply is also introduced. This section gives details of chip selectand circuit board design.The fifth part describes tests and experiments. Experiments on signal to noiseratio and long-term stability are conducted. Then, using soil samples, thespectrometer gives the accuracy of soil nutrients analysis.In the end, contents of this paper are summarized, and some suggests forimprovement are given.