| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To precisely detect the flow rate in the pulsed state including a large reverse flow. <P>SOLUTION: Upstream temperature sensors 6 and 7 and downstream temperature sensors 8 and 9 are formed by sandwiching a heater 4. Parallel resistors 10 and 11 are formed outside a thin film (hollow 26), and are connected to the downstream temperature sensors 8 and 9 at contact points 43 and 45. The upstream temperature sensors and the downstream temperature sensors are respectively arranged on the four sides of the bridge circuit 4 so that the same element is not neighboring, and the part between electrodes 42 and 44 is balanced when there is no flow. When the normal flow 20 flows, although the upstream temperature sensors are cooled and the downstream temperature sensors are influenced by the heater, the apparent change is small, and the electric potential difference between the electrodes 42 and 44 becomes large. When the reverse flow 21 flows, although the downstream temperature sensors are cooled, the apparent difference is small, and the temperature of the upstream temperature sensors is raised by the influence of the heater. As a result, because the flow rate characteristic is obtained in which the flow rate characteristic of the reverse flow is compressed with respect to the flow rate characteristic of the normal flow, the detection of the reverse flow can be performed with the voltage range narrower than that of a conventional technique. <P>COPYRIGHT: (C)2004,JPO&NCIPI</p> |
