| The Portable multi-channelγ-ray spectrometer is mainly used in the filed directly to measure the content of U, Th, K in the rocks'surface, soil, ore. And obtaining the information of relevant nuclide. It is widely applied to geological mapping,the exploration of radioactive minerals and non-radioactive mineral, hydrogeology and engineering geology, the monitoring of construction materials and environmental and so on.Since theγspectrometer needs to have the function of adopting the signal of filed spectrum and processing the on-site data, also consider the special application environment,the requirements of the instrument's portability,stability and operability is high.This subject of design make PDA as the host of gamma spectrometer with the function of data acquisition and processing,Bluetooth and USB technology is used in the design to provide a variety of communication interfaces while ensuring the performance of the instrument.Based on this,application of the instrument has been some expansion.The author mainly studied the subject about the hardware and embedded software components in this subject,hardware circuit including detector,analog circuit,digital circuit and power circuit. The NaI scintillation detector used in the research makesγ-ray convert to the electrical pulse signal through PMT,then the electrical pulse signal is sent to analog circuit part to be processed.Analog circuit including bootstrap circuit,pole-zero cancellation circuit,linear amplifier circuit,programmable amplifier circuit,filter circuit,baseline recovery circuit,slider circuit and Multi-channel pulse height analysis circuit. The Multi-channel pulse height analysis circuit including low threshold detection circuit, peak detector circuit, peak hold circuit, analog-digital conversion circuits and logic control circuit.The analog circuit is mainly responsible for the magnify and shaping of the signal,and convert the peak of pulse signal from analog value into digital value.The use of slider circuit improve the differential nonlinearity of Multi-channel pulse height analysis circuit.The digital circuit is mainly responsible for the logic control of analog circuit and data reception,compound and sending.The design provide three method to transport data,they are serial port,Bluetooth and USB interface.The power circuit adopt two ways to supply power,namely battery-powered and USB-powered,in order to make the equipment with the feature of low power,the power supply under the control of the microcontroller,using MOS tube off function,According to the needs to control the supply status of analog circuit and Bluetooth module. Embedded software section read the data information from CPLD through int0,According to the needs of the design, makes the digital value execute the operation of 64 channel compounds to 1 channel,also establish the communication protocol between the design and host computer software.Combining different data transmission channel(serial port,Bluetooth and USB) for different transmission protocols,to make sure of the right transmission of 1024 channel data information.
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