Research Of Intelligent High Resistance Gas Sensor Based On ARM

Along with the quick development of national economy as well as the continuous improvement of living standard, gas sensors has been widely applied in the fields of food industry, environmental test, industrial and agricultural quality control, medical sanitation, etc. With the rising demand for gas detection, gas senor and their discrimination technology have already drawn a lot of attention. So, the cheap measuring devices with good performance have been the new direction of measurement field.Based on this research background, with the knowledge about the mechanism of the gas sensitive material and work principium of the gas sensor, we designed a new equipment of gas measurement in this thesis. This system is applied LPC2131 with ARM7 as the processor, using its powerful data calculation and control capability of ARM, we designed a circuit which can measure the gas concentration. LPC2131 which integrates many hardware functions inside, so it reduced the cost and minimized the setting volume.The design of this testing equipment mainly includes two parts, hardware and software. The hardware part consists of three major parts, signal collection circuit, ARM system module circuit design, LCD module design. The software part consists of following parts as the design of channel choosing program design, A/D transformation program design, single processing program(arithmetic), LCD module program design and PC application program design.The circuit of this device is constructed according to the theory of gas sensor's resistance, which is changed with the variation of gas concentration. But from the experiment date we know that the relation between the collection signal and gas concentration is nonlinear. So, in some occasions needing high precision and high speed, the concentration can not simply be get by general table-searching method. We need adopt an effective arithmetic to realize the high precision change. This equipment adopts the Polynomial-Match combining"Return to Ten"and"Normalized."The operation process of this arithmetic is very simple, but it can achieve high precision. So, the arithmetic quite fits this equipment.By actual testing, this equipment can measure gas concentration exactly. The precision of this equipment is kept within±1.5%. The new equipment is featured by high-sensibility, compact size, simple and low consumption and so on.