| 摘要 |
<p>PURPOSE:To prepare the title flowmeter having high response and a simple structure at a high automation rate by providing a heating resistor and an air temp. measuring resistor. CONSTITUTION:A current is supplied to a heating resistor 1 by a power transistor 11 to heat said resistor 1 and control is performed so that the temp. of the heating resistor is always higher by definite temp. than that of an air temp. measuring resistor 6. At this time, only a current weak enough to be capable of neglecting the generation of heat is allowed to flow to the resistor 6 and, by this method, said resistor 6 is used as one for detecting and correcting the temp. of sucked air. When an air stream impinges on the resistor 1, a drive circuit is operated to perform control so as to always make the temp. difference between the resistors 1, 6 constant. This operation is performed by applying feedback so that the voltage obtained by dividing the voltage difference between both terminals of the resistor 1 by resistors 14, 15 becomes equal to the voltage obtained by amplifying the voltage drop of a resistor 13 generated by the current flowing through the resistor 1 by an operational amplifier 9. Therefore, when an air flow rate is changed, the current flowing through the resistor 1 is changed and an air flow rate is measured on the basis of the voltage drop appearing in the resistor 13.</p> |
