| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a heating resistor-type air flow rate measuring apparatus whose measuring accuracy is ensured and whose noise is reduced by a method wherein the AC component of a reverse-direction detection signal is added to a forward-direction detection signal and the AC component of the forward-direction detection signal is added to the reverse-direction detection signal so as to offset a noise component. SOLUTION: Air-flow-rate detection parts 8, 18 detect heating currents of heating resistors 1, 11 by means of resistances 3, 13, and they output a forward-direction detection signal V2 F and a reverse-direction detection signal V2 R. The two signals are characteristic-adjusted by characteristic adjusting circuits 21, 22 so as to be output as a forward adjusting signal VOF and a reverse adjusting signal VOF. After that, the adjusting signals VOF, VOR are adjusted by a comparator 29. The signal which is larger is selected by a switching circuit 30 as a forward-direction offset output signal Vout F or a reverse-direction offset output signal Vout R. A differential amplifier 31 inverts a voltage when a reverse current is detected, it amplifies the forward- direction offset output signal Vout F or the reverse-direction offset output signal Vout R as an output signal, and it outputs a flow rate signal VG which contains the direction component of an air flow.</p> |
