Investigation And Design Of The Testing Device Based On LPC938 For The High Resistance Gas Sensor

The economic development makes people to care about their lives more and more。Peoplewant to measure the harmful gas more easy。In our country, the gas sensor develops quickly,but the gas sensor testing device develops slowly because of the high resistance of the gas sensorand the compact interface of the testing equipment. Knowing about the mechanism of the gassensitive material and work principium of the gas sensor, we have designed and investigated atesting device for gas sensor that has high resistance. This device is used in our laboratory.We apply the PHILIPS LPC938to the testing circuit in this design instead of the C51 singlechip, LPC938 which integrates many hardware functions inside of the C51 single chip, LPC938which integrates many hardware functions inside, so it reduced the cost and minimized thesetting volume. At the same time, we used the lithium cell as the power, it was convenient for theuse and popularizing of the testing device. Combining the powerful data calculation and controlcapability of LPC938 with the high resistance characteristic and mechanism of gas sensitivematerial, this testing device makes up the sampling circuit and PWM. It can display the gassensor'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 thedrive programming of the chips and the whole program, using the debug online function of theLPC938 ,we debugged the whole program succeed .We used the LPC938 as the microcontrollerto control the power's voltage instantly and the gas sensor's working temperatures and tomeasure the thin film's resistance. After the calibration of the gas concentration and component'sresistance, we display the tested gas concentration and intelligenting the gas sensor by providinga friendly user's interface with an alarming function.Thin intelligent sensor has a wide dynamic testing range and high precision, lowconsumption, low cost, small volume and good reproducibility, it can satisfy the gas sensitivetesting need totally.