Design Of Multi-channle Pulse Amplitude Analyzer Based On ARM

With the rapid development of atomics science and electronic technology, thesurvey and analysis of radioactive spectrometry is becoming more and more importantin various fields. The nuclear energy spectrometers are becoming smaller in volume,lighter in weight, higher in performance, lower in power loss and expense. As a veryimportant part of the nuclear energy spectrometer, the performance of Multi-channlepulse amplitude analyzer influences the results of radioactive survey and analysis.Nowadays, plenty of Multi-channle pulse amplitude analyzers of high performanceare foreign products. Most of our domestic instruments cannot compete with foreignproducts for their large volume, high power consumption, without automaticallylocate function, and they could not adapt to indoor, outdoor, and many otherapplications. Based on this situation, this subject designed a portable Multi-channlepulse amplitude analyzer based on32bits embedded microprocessor S3c2440ofARM920T core and embedded Linux operation system.The hardware includes shape amplifier, Multi-channle pulse amplitude analyzerand S3C2440’s periphery circuit.The shape amplifier includes pole-zero cancellation circuit, Pulse amplifier,integrating filter and base line restorer. The pulse amplifier is a two-stage amplifierdesigned by2integrated operational amplifiers CA3140, and it can amplify inputsignal by up to a dozen times. The integrating filter can convert the input signal toquasi-Gauss wave with the two-stage active integrating filter designed by Sallen-Keyand a passive filter. The base line restorer improves the quality of the signal and theperformance of instrument by removing the Baseline Drift.The Multi-channle pulse amplitude analyzer includes pulse amplitudediscriminator, peak detector, logic control circuit and A/D converter. The amplitudediscriminator eliminates the interference of low energy noise pulse and detects the pulse peak with high-speed comparator LM311. The peak detector can hold andexpand the peak amplitude to A/D convert time with CA3140and LM311. Logiccontrol circuit designed with2chips of74CH74controls all the circuit work togetherwith right scheduling. The A/D convert circuit quantizes the amplitude by connectinga high-speed12bits A/D convert chip ADS774.S3C2440’s periphery circuit includes LCD and touchscreen interface circuit,electric power supply circuit and reset circuit. The LCD and touchscreen interfacecircuit designed by TFT-LCD Module of3.5-inch Touch Panel (LTV350QV_F04Type) manufactured by SUMSUNG electronics co. ltd. The electric power supplycircuit was designed by LM1117of high performance at low cost. The reset circuitsupervises electric power supply circuit effectively witch designed by the chip ofMAX811.The software platform of the system is Embedded Linux operation system.Firstly, BOOTLOADER U-boot and Linux kernel2.6.20was ported on the base ofthe hardware to develop the root file system of CRAMFS and YAFFS. Secondly, Theprogrammes of A/D convert driver, of touchscreen driver and of LCD driver werealso written. At last, the analysis of spectrometer software was designed anddeveloped by QT/Embedded GUI tools. The function of the software includes dataacquisition, graphic display, date management, energy calibration, data calculatingand analysis.The Multi-channle pulse amplitude designed in this subject based on the combineof ARM technology and Embedded Linux operation system can work at fullspectrometric of1024channels surveying with display graphic by LCD. Theinstrument can be operated by touch screen. It is small in size, light weight, lowpower consumption, easy to carry, measurement precision. The system performancetest indicates that this instrument has advantage of good linear, stable performance,and it can be used in practical fields. The research of this subject has value forreference in introducing ARM and Linux technology to the study of the portablenuclear energy spectrometer.