Data Controller Design Of X-Ray Diffraction Instrument

X-Ray diffraction instrument adopts X-Ray irradiating the different substance to produce the different stripe due to their different crystal structure. It is to research crystal structure not the types and the contents of contained elements. Data controller is the main part of the X-Ray diffraction instrument, whose measuring and controlling objects is as following:Voltage and current measurement of X-Ray generator high DC voltage working :Voltage measurement: convert part of analog voltage into digital able to be processed by computer.Current measurement: convert analog current of sampling resistance into digital able to be processed by computer.Voltage controlling: analog voltage output of D/A with computer digital signal to control anode voltage of X-Ray generator. Current controlling: analog voltage output of D/A with computer digital signal to control cathode filament voltage of X-Ray generator.Diffraction angle measurement unit: It controls linkage set of sample table ,the device used for measuring sample and X-Ray focusing slot system through controlling two or more groups of step motor and controls X-Ray source through controlling slot shutter and tests linkage set's upper limit and lower limit.X-Ray intensity recording unit: To test and measure the counter tube window voltage amplifier, impulse magnitude analyzer and impulse counter.Since X-ray cannot be measured directly, it must be firstly converted into electrical signal able to be measured and then convert into digital signal through counter. Usually flash counter, which is composed by flash piece and multiplier phototube, is used as a detector. When X-ray eradiate into flash piece, a number of visible photons are engendered in flash piece, and the number of visible photons is in direct ratio with the energy of X-ray photons. Photons of flash piece, measured and amplified by multiplier phototube, form the output pulse of detector. The amplitude of detector output pulse is very small(about several mV), so it must be amplified by proportional amplifier in order to reach amplitude of 5V. Pulse signal of proportional amplifier is sent to counter after reduced noise by window voltage comparer.According to the principle of X-Ray diffraction instrument and measured or controlled objects, this paper mainly discusses about how to design data controller of the X-Ray diffraction instrument. The main points are:Discuss about measured and controlled objects of X-Ray diffraction instrument base on analyzing principle and structure of X-Ray diffraction instrument. According to the measured or controlled objects, propose the main structure of data controller of the X-Ray diffraction instrument, which adopts multi-CPU bus system integration technology, say, a multi-CPU controller. And each CPU controls one module, and each module is an independent computer system, however they are related through the bus on the motherboard. Present further the design scheme of bus standard,standard communication code and command,main control module,step motor module,testing module,AD/DA module, I/O module,relay module.Research the operating flow of X-Ray diffraction instrument, communication protocol and communication flow between the main control module and the upper layer manage computer, between main control module and each sub-module, drive flow of step motor, counter method, choosing window voltage, choosing high voltage for multiplier phototube.Summarize the technical specifications of data controller of X-Ray diffraction instrument. Give partly performance testing and sample experiment results, which is analyzed to imply the shortage of data controller of X-Ray diffraction instrument. Then propose the improvement scheme primarily.