The Manufacture Of Gas Sensor Based On Hall Effect

In the Hall effect, Hall electromotive force is not only related to the current density, magnetic field and the distance of the poles, but also to Hall coefficient directly. Hall coefficient depends on electronic concentration and the relative values of empty hole concentrations and their migration rate in the semiconductor. Semiconductor materials was laid on the base, and the corresponding electrode was lead to. The semiconductor material has selective adsorption to the gas that changes the electronic concentration which also raises Hall coefficient ,corresponding changes the export of Hall electromotive force ,so the gas sensors which is based on Hall effect was made.The preparation of material and the structural design were introduced in this article. In fact of the preparation of material, Nanometer WO₃ was synthesized in a novel method by gas-state reaction with tungsten filament. Further more, we designed a new type gas sensor based on Hall effect. Then we made nanometer WO₃ into these type gas sensors. This novel components don't need heating device, so the entire structure is quite simple, and the output signal is direct voltage which is enlarged and processed rather convenient. The gas sensing measurement results revealed that these sensors have a certain response to NO₂ with good response characteristic. To 40×10-6NO₂, with good response time of 36s and recovering time of 45s, the sensitivity is 3.2 and changes with the density of NO₂. So the conclusion is that this gas sensor based on Hall effect is a prospective and novel gas sensor.