Improving Design Of The Circuit System Module Of The Portable Near-Infrared Spectrometer

Near-Infrared Spectroscopy of modern technology is considered as the fastest growing and the most striking spectral analysis techniques since the 90's, and is known as the Giant of analysis. Near-Infrared Spectroscopy is widely used for its characteristics of high analytical speed, low cost, non-destructive and non-polluting, etc. Recent years, portable near-infrared spectroscopy devices have become more attractive. Our lab have spent several years on developping the portable near-infrared spectrometer prototype, and made the dream of field workers that"take analytical laboratory outdoors to do experiment" come true. The paper analyzes the inadequacies of the Prototype and describes the improvements, and realizes the improvements in modularity.Modular designing is to perfecet and develop the traditional designing methods. Considering the electronic products varieties, specifications, styles and high-performance requirements, such as diversity on the market, traditional electronics and mechanical designing methods has been out of date. While modular designing will enable electronic products to stage the designing and manufacturing to high-efficiency and high-performance. At present, the idea of modular designing has infiltrated into many domains, such as machine tools, deceleraters, household appliances, computers and so on. The meaning of the modular designing prevailing in the world can be expressed as: modular designing is to design the same functional unit with different modules of different uses or properties, while we can replace the modules. From the systemic point of view, the modular designing is a entire process that builds systematic modulars and applicates modules into a system by the method of decompositing and compositing modularized object. Functional analysis of products is a good basis for a good modularized system, so as to fix the products' features and main parameters. Refer to the structure of existing products, do the functional analysis to the new products, complex issues will be broken down into simple and easy-implement sub-questions (sub-function). By the correlating function analysis, we can combine the sub-functions into more powerful functional modules. Therefore, the related study and analysis is good for deviding functional modules, connections, etc.In power system designing of the portable electronic devices, the challenge is how to improve the product's performance and prolong the batteries'working time. Higher power requirements of power management technology were put forward for the fast innovation and development of portable electronic equipments. While designing portable electronic devices, we should consider not only the parameters of the power itself, but also take many aspects such as electrical design, power management design, PCB design, EMC design, thermal design, security design, and so on into account. This essay introduces the functions and designing route of the power module, and then refers to the management of lithium batteries, the charging protection of lithium batteries and the power PCB designing technology.This essay can be divided into seven chapters, and its structure and contents are as follows:Chapter I deals with the principles of near-infrared spectroscopy technology, applications, and modular designing study programs, analysis of the development of portable near-infrared spectroscopy of the feasibility and necessity.Chapter II from the system point of view, put forward a design prototype to improve the overall program.Chapter III analyzes the inadequacies of the prototype, through calculating the circuits'parameters, by comparing with the original prototype, the new one has improved the signal to noise ratio greatly and it is more stable.The circuits include sensoring and sampling circuit, band-pass filter, phase-shifting circuit, synchronous integral circuit, in-phase amplifier, phase-sensitive detecting circuit, and inverted-phase filter circuit. The essay analyses each part of the circuits, so as to make each of them suitable for the system. Experiments indicate that the new circuits bear more stability and lower noise, furthermore, it is more reliable in absorption of minerals indicated by the analysis software.Chapter IV outlines the functions of data acquisition circuit, the designing of the interfacing circuit among SCM, AD, USB and stepper motor controller, discusses the noticed points of modulizing, theoretical analysis and experimental results show that: this method can be applied to near-infrared spectrometer interface circuit, and able to completely replace the wiring and achieve better results.Chapter V designs the near-infrared spectroscopy of whole power management module and an independent power source, the lithium battery-powered and designs battery-protection circuit and voltage monitoring circuit, which are used to supply power for light, stepper motor, anlog circuit and ARM section. The essay has designed batteries charging-protection circuit and the voltage monitoring circuit, which monitors the batteries at any moment. After testing, power supply can meet the requirements of stability, low ripple and not be interfered with each other, PCB design and thermal power to do a simple design. Chapter VI tests the power performance and the optimized circuit module, has done comparative analysis to multiple sets of collected data of whiteboard, the contents include smoothness, wavelength stability and reproducibility. We have gained better parameters and demonstrated the reliability of the power management module. Through the comparative analysis to spectral data with PIMA which is made by Australia to verify the correctness of the functional prototype products.Chapter VII summarizes the main results and weaknesses of the essay, makes further suggestions for improvement.