| 摘要 |
<p>PURPOSE:To improve resistances to contamination by detecting the changing amount of an output signal which amount changes corresponding to the attaching amount of dusts to a hot wire air flow meter. CONSTITUTION:A flow detecting portion of a hot wire air flow meter is placed in a windless condition, with the power switch turned OFF. Therefore, the hot wire is cooled to be equal to the air temperature. Then, the power switch is turned ON to apply a fixed voltage to a heat generating resistance. An output signal of the hot wire air flow meter is detected a predetermined time later after the application of voltage. As more and more dusts attach to the flow detecting portion of the flow meter, the heat capacity of the detecting portion is increased. Therefore, the output signal indicates a larger value than the initial value. Accordingly, by comparing the output signal when dusts attach to the flow detecting portion with the initial value, a correcting value for correcting the measurement error is calculated depending on the contaminated condition of the heat generating resistance.</p> |
