| 摘要 |
<p>PURPOSE: To measure an average air flow rate accurately even for a pulsating air flow accompanying a reverse flow by determining the average air flow based on the direction of air flow determined by the magnitude of signal delivered from two heating elements and the air flow rate determined by a signal delivered from a heating element having higher heat dissipation. CONSTITUTION: The potential (flow rate signal) at the lower end of a downstream side heating element 3 having smaller area is lower than that of an upstream side heating element 2 having larger area. A differential amplifier 27 regulates the amplitude of potential such that both potentials are equalized when the air flow rate is zero. When the potentials are compared by means of a comparator 28, a signal from the element 2 is higher than that from the element 3 and a flow direction signal is obtained. An analog switch 31 is operated by the signal to regulate the characteristics of potential (output signal) at the lower end of the element 2, through differential amplifiers 29, 30, such that the potential increases with the forward air flow rate but decreases with the reverse air flow rate. The signal is inputted to an engine control circuit 100 where an average air flow is determined.</p> |
