Weak Signal Amplifier And Signal Transmission System For Apple Internal Quality Nondestructive Testing

In this paper,it mainly study the circuit design of the weak signal amplification in the process of apple nondestructive testing.The main contents of this paper are as follows:Nondestructive testing technology(NDT)is a modern detection technology to obtain the relevant performance index of the tested object without destroying the character and composition of the tested object.In recent years,its application in the field of food purchase and processing is more and more.It has certain research significance and application value for classification of apple by nondestructive testing technology obtaining apple internal quality.In this paper,the weak signal within the apple under nondestructive testing technology is as the of study.The different methods are used to amplify the weak signal.And the noise caused by the amplifier circuit and the information transmission of the signal are studied.The main contents of this thesis include:(1)The paper adopts two circuit design schemes,namely transistor amplifying circuit and integrated operational amplifier circuit.It will amplify the micro-volt and millivolt small signal to voltage level.Based on the requirements of high gain,the two schemes adopt the single stage cascaded coupling multilevel amplifier circuit form.Due to the influence of preamplifier noise on the performance of the whole circuit,the paper focuses on the design of the preamplifier circuit.The transistor amplifier prestage adopts the differential structure,and combined with the NPN and PNP transistor common emitter amplifier as well as complementary symmetry structure,to achieve the design requirements of the preamplifier 1170 times.The operational amplifier circuit adopts the instrument amplifier structure,and uses the chip TLC2652 and OP07 to form the three operational instrumentation amplifier,which can achieve the design requirement of the preamplifier amplifier 100 times.(2)Aiming at the noise problem in the amplifying circuit,different noise sources are analyzed and corresponding noise suppression methods are proposed.Firstly,the noise sources of amplifying circuit are analyzed,including the component's own noise,power frequency noise and background noise.Corresponding noise suppression methods are proposed for different noises,so that the signal can be effectively amplified and transmitted without distortion.Finally,the noise model is used to analyze the preamplifier stage of the transistor amplification circuit and the integrated operational amplifier circuit.The paper need choose a more suitable design by calculating the RMS value and comparing to the calculation results.(3)Firstly,Bluetooth hardware and software interface based on MCU is designed in this paper.On this basis,aiming at the design of Bluetooth data transmission system,two aspects are studied,which are hardware design and system software design.System hardware design includes: hardware design of MCU and hardware design of the PC terminal.System software design includes: software design of MCU and software design of the PC terminal.The research adopts the integrated operational amplifier circuit and completes the micro-volt and millivolt signal amplification to the volts level.By simulation experiments and actual circuit testing,the circuit achieves undistorted amplification of weak signals.Wireless transmission of information is realized by using Bluetooth technology.It provides the basis for further research on apple non-destructive testing and grading.