Investigation And Design Of The Testing Device Based On ARM For The High Resistance Gas Sensor

The economic development makes people to care about their lives more and more, People want to measure the harmful gas more easy. In our country, the gas sensor develop quickly, but the gas sensor testing device develop slowly because of the high resistance of the gas sensor and the compact interface of the testing equipment. Knowing about the mechanism of the gas sensitive material and work principium of the gas sensor, we have designed and investigated a testing device for gas sensor that has high resistance. This device is used in our laboratory.We apply the increasingly popular ARM technology to the testing circuit in this design instead of the C51 single chip, LPC2131 which integrates many hardware functions inside, so it reduced the cost and minimized the setting volume. At the same time, we used the lithium cell as the power, it was convenient for the use and popularizing of the testing device. Combining the powerful data calculation and control capability of ARM with the high resistance characteristic and mechanism of gas sensitive material, this testing device makes up the sampling circuit, heating circuit and PWM, it can display the gas sensor's resistance and the gas density whereabouts, it fulfills the need of gas sensor test.The software is designed on the basis of the hardware, with the set up code, we designed the drive programming of the chips and the whole program, using the debug online function of the LPC2131,we debugged the whole program succeed。We used the LPC2131 as the microcontroller to control the power's voltage instantly and the gas sensor's working temperatures and to measure the thin film's resistance. After the calibration of the gas concentration and component's resistance, we display the tested gas concentration and intelligentize the gas sensor by providing a friendly user's interface with an alarming function.This intelligent sensor has a wide dynamic testing range (1M----500MΩ)and high precision(0.5% at least), low consumption, low cost ,small volume and good reproducibility, it can satisfy the gas sensitive testing need totally.