The research of flow sensor based on application of automobile

The thermal film flow sensor has been researched. The membrane is made of multi-film with high mechanical robustness and low cross direction thermal conductivity. The temperature distribution of membrane has been simulated; the variation of temperature on membrane has been analyzed at different flow rate. By comparing the results of experiment with the results of simulation, a conforming conclusion is obtained: at low flow rate, the falling of temperature in upstream by cool effect is remarkable, the temperature in downstream increases slightly, and the temperature difference between upstream and downstream is notable. With the flow rate increasing, the temperature in upstream distance reaches saturation, and because there is a whole cool effect on the chip at high flow rate, the temperature in downstream distance begins to decrease slightly. Therefore, the flow measuring range obtained by temperature variation of distance measuring resistor is small. Two pairs of measuring resistors are placed in upstream and downstream respectively, which enhances the measuring precision and widens measuring range. Comparing with single output voltage value, the superposition value is high a lot. The peak value of single voltage signal reaches 15. 7mV, whereas, the peak value of superposition voltage can reach 28. 6mV. Meanwhile, measuring range has been broadened.