| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a thermal flow rate sensor for restraining influence due to the fluctuation of a fluid temperature and stably and accurately measuring a flow rate. <P>SOLUTION: Devices 16A, 16B at base and tip sides are arranged to straddle a forward passage 11A and a return passage 11B in respective U-shaped channels 11. A base edge side transistor 42A indicates temperature characteristics according to an average temperature at a highest temperature measurement location A and a lowest temperature measurement point B, and the oscillation circuit A oscillates with a phase accordingly. A tip side transistor 42B indicates temperature characteristics according to the average temperature at measurement locations B, C at a middle temperature, and the oscillation circuit B oscillates with a phase accordingly. The average temperature changes nearly at a coincident temperature even if a fluid temperature varies without heating by a heating transistor 43B. Therefore, the inversion interval in the heating time of a heating transistor appearing as an interval for inverting a signal outputted from a CMOS gate 56 becomes proportional to the flow rate of fluid, thus avoiding influence due to the variation of the fluid temperature and stably and accurately measuring the flow rate. <P>COPYRIGHT: (C)2004,JPO</p> |
