| With the increasingly serious environmental pollution and increase people's awareness of environmental protection, people pay more attention to the quality of their living environment, particularly indoor air quality. From the health point of the radioactive ,radon and its decay daughter widespread in people's living space.When people is long in the environment with radon, both inhalating air with high radon and drinking water containing high level of radon easily lead to cancer place. Therefore, the air radon monitor in the world scientific community and media is hot topic. Scientificly comprehensive analysis of living environment, radon potential hazards to human health, to identify people living space radon source, and come up with effective and feasible protective measures, are of great pratical value for improving the quality of people's lives and people's living environment.Radon (Rn) generated by the natural decay of radium is only natural radioactive inert gas, colorless and tasteless,exist mainly in most of the soil and rocks (especially granite) .Radiation decomposition will produce radon gas. It is a naturally occurring radioactive gas harmful to people's health.When people breath, radon and its progeny with the air enter the body.When people inhaled it , the radon daughters deposited on the airway surface constantly, in the local area accumulation of human tissue formation over the long term exposure. Such hazards in indoor and underground areas is even more serious, underground home radon concentrations much higher than the ground-room is about 40 times.In order to reduce and control the dangers of radon on the human body, scientific and accurate measurement of radon concentration in the environment has become an important measure of radon gas monitoring. Measurement of radon in the living environment is a complicated issues ,being related to nuclear science, earth science, environmental science and many other subjects .Furthermore it is related closely to nuclear technology, electronic technology and computer technology . Low power consumption, simple and easy to maintain, versatile, easy to use, high cost performance, more humane operation of radon devices is the inevitable trend of future development.This thesis describes a grid pulse ionization chamber-type radon monitor that can monitor ambient air concentrations of radon and its daughters. The device is with the measurement of high sensitivity, accuracy and good stability. The radon monitor can be widely used in radon levels in ambient air monitoring, building interiors, and residential housing internal investigation of radon pollution. The instrument adopts new grid pulse ionization chamber at atmospheric pressure.Because the air in ionization chamber communicate with the outside world, an environment free of radon gas can be directly spread to the chamber.Under the direction of electric field , the electrode collects charged particles and generates pulse signal.Then,the signals is transmitted to the microprocessor system for count handling, storage and display.If it is necessary, the measure data can be uploaded to the computer through the USB interface,displayed, analysesed and processed.The instrument adopted a cylindrical mesh pulse ionization chamber detector at atmospheric pressure, which is designed wih reasonable shape and size, with good detection efficiency and sensitivity of the measurement volume.Preamplifier of signal amplification and screening circuit selected high impedance low noise FET amplifier OPA604 integrated chips, replacig the common FET amplification, it effectively improve the circuit stability and anti-jamming capability. Measuring radon control system selected CY68013A chip which is introduced by Cypress.Micro-controller system achieve to control real-time clock, LCD display and buttons, as well as program and data memory settings and control operations.Real clock selected Real Time Clock Chip DS1302 chip which is lauched by DALLAS in the United States launched .The chip is a high-performance, low power, real-time clock chip with RAM.It can be years, months, days, weeks, hours, minutes, seconds automatic timing.Then the system realizes to In order to maintain accurate time information as saving the measurement datas. In human-computer interaction, the system selects JD12232 LCD display yellow as shown in black type, designs 4 simple keys including menu, up, down and OK,achieving simple and convenient man-machine dialogue. Data memory chips are CAT24WC256 chip which is 256K-bit Serial CMOS structure E2PROM, internally containing 32,768 bytes.Each byte is 8 bit low power data storage chips.By calculating the size of stored data structure,the system can achieve a storage group 3000 measurement data capacity. Selection of highly efficient switching power chip to supply the system,it demandes instrument's requirement of low power consumption.Becaus most computers do not be configured RS-232C Serial interfaces now,the system select USB interface to transmit datas with the computer .And the micro-control chip CY68013A integrates USB interface and realizes easily to transmit measure datas through the USB interface with computor.In the application procedures, using Visual C++ 6.0 and the MFC object-oriented language developes data transmission applications.The software interface is simple to achieve the transfer measurement data and delete measurement datas functions.After a year of research and experimental verification, mainly in the following innovative research results are:(1) In the choice of detector, using atmospheric air mesh pulse ionization chamber which is cylindrical mesh structure.The environment free of radon gas can be directly spread to the high pressure chamber, with a clear size and sensitivity good detection efficiency.(2) At screening signal amplification circuit,, the signal pre-amplifier selects high impedance low noise FET amplifier OPA604 chip, replace the common FET amplification, meet high input impedance requirement of preamplifier , effectively improve the circuit stability and anti-jamming capacity.(3) At the memory chip,the system selects CAT24WC256 data memory chip which is 256K-bit Serial CMOS E2PROM, containing 32,768 bytes of internal self-defined data structure design of measurement,.According to the size of stored measurement data structure calculation, it can store up to 3000 measurement datas.(4) For the majority of computers are not configured the current RS-232C serial interface, according to the system need to select the USB interface to computer data transmission, the system achieves to transmit measurement datas with computor through the USB interface , and develops the corresponding data transfer applications software.
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