The Study Of High Sensitivity Of Portable Gas Detection System Based On NDIR Principle

With the rapid development of the coal industry, coal production in China is increasingly prominent on security risks, mainly in the coal mine gas exceeding seriously. Therefore, in the production of coal mine safety, reliable, accurate, real-time on-site monitoring of gas (CH4is the main component) concentration is an important means of preventing the occurrence of coal mine gas explosion. But currently the methane detector’s accuracy, stability is very low. In view of this, on account of the theory of NDIR and assimilate strength is a function of the concentration of methane, I conduct a study design about portable methane gas detection system.The whole system includes pyroelectric detector and the main circuit. Pyroelectric detector comprises an optical cavity, infrared light, temperature compensation thermal resistance and erasable read-only memory (EEPROM); The main circuit includes a power supply circuit, a microprocessor system (including signal acquisition), lamp drive circuit, signal filtering and amplification circuit, data download circuit within EEPROM, the crystal timing circuit, the digital display circuit, liquid crystal display circuit, RS232interface circuits, data storage and sound and light alarm circuit. Pyroelectric detector uses OP17-IRcel’s miniature infrared gas sensor integrated temperature compensation module. We can read and change the parameters of erasable read-only memory of the sensor to calibrate and zero the sensor probe.Microprocessor is MK60DN512ZVLL10model minimum system of Freescale Semiconductor’s32-bit Kinetis K60family of microcontrollers. When a dual-channel signal values and temperature values which are outputted by the sensor have filtered and amplified, these data will be acquired and processed by16bits microprocessor’s ADC and finally saves the parameters and displays the current concentration. When the staff come out from the mine, connecting to a computer via RS232serial to download EEPROM’s the parameters and test data, then to analysis and set the concentration thresholds.Under laboratory conditions, we have a gas absorption experiment for the system, having a spline fitting for the experimental results of the data error analysis and calibration. The results proved the high sensitivity of portable gas detection system based on NDIR principle within the error range has a good repeat resistance, high accuracy, good stability.