| 摘要 |
<p>PURPOSE:To enhance accuracy in the detection of flow rate of sucked air by deciding whether air is flowing forward or reversely. CONSTITUTION:A first heating resistor 29 and a second heating resistor 30 are formed, respectively, in the upstream and downstream on an insulating board. Variation of each resistance RH1, RH2 is inputted, in the form of flow rate voltage V1, V2, to an average value circuit 35 which delivers a flow rate average value voltage V3 to a selection circuit 43 and an inverting circuit 42. A comparator 34 compares the flow rate voltages V1, V2 and delivers a direction detection voltage Va to the selection circuit 43. If V1>V2, V3 is outputted as a flow rate detection signal and if V1<V2, V3 is inverted to be V3' through the inverting circuit 42 and outputted. Consequently, the flow rate detection signal can be detected at high response along with the flow detection.</p> |
