| 摘要 |
<p>PURPOSE:To accurately detect a flow rate even when the circumferential temp. is changed by adding temp. compensating function to a circuit for processing a flow rate signal detected by a hot wire. CONSTITUTION:A hot wire control circuit 2 for controlling the temp. of a hot wire 1 to generate the output signal of the hot wire 1, an amplifying circuit 3 and a frequency converter circuit 4 for converting an analogue signal to a frequency signal are provided. In the temp. change of the hot wire 1, there are offset at an air flow rate of 0 and a gain showing the change component of the output from the hot wire with respect to a change of a unit air flow rate and temp. compensation is necessary. Since an offset temp. compensation circuit 31 having offset temp. compensating function is provided to the amplifying circuit 3 and a gain temp. compensating circuit 41 having gain temp. compensating function is provided to the frequency converter circuit 4, the effect of the circumferential temp. is extremely reduced. Therefore, even when the circumferential temp. is changed, an accurate flow rate can be detected.</p> |
