| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a thermal air flowmeter in which the dynamic range is widened while reducing noise and the reliability of dustproofness is enhanced by providing a pair of heatting elements, respectively, on the upstream side and the downstream side of a temperature measuring element. SOLUTION: In a measuring element 1, upper surface of a semiconductor substrate 2 is coated with an electric insulation film which closes the upper surface side of a cavity 3. A pair of heating elements 5, 6 are arranged, respectively, on the opposite sides of a temperature measuring element 4 in the upstream and downstream of an air flow. The heating elements 5, 6 are fed with currents for heating up the temperature measuring element 4 to a temperature higher by a predetermined level than the temperature of an air temperature measuring element 7. In order to control the temperature measuring element 4 to have a temperature higher by a predetermined level than the temperature of an air temperature measuring element 7, the air flow rate is measured by taking advantage of the fact that the heating current to be fed to the heating elements 5, 6 increase when the air flow rate increases. Direction of the air flow 9 is also detected from the temperature difference between the heating elements 5, 6.</p> |
