| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a flow meter with little measuring error even during pulsating of air flow with a simple constitution by correcting air flow rate signal at the output of a bridge circuit, based on the potential difference between a first and second resistors connected in series. SOLUTION: A sensor circuit 210 forms a sensing part of the thermal air flow meter which is connected to a power source 21 to heat a heating resistor 211 at a fixed temp. and transfers heat generated according to the flow rate, thereby measuring the flow rate of air flowing on the heating resistor 211. An error corrector composed of a microcomputer 220 receives an output signal Vin from the sensor circuit 210, converts it to a digital value, using an A/D converter 221, corrects the error according to correction data prepared in a rewritable memory 223, using an arithmetic circuit 222, and outputs a voltage value corresponding to the output of the sensor circuit 210 to an engine control unit, using a D/A converter 224. The sensor circuit 210 and the error corrector composed of the microcomputer 220 form an air flow rate measuring apparatus 20, including a power circuit 23 generating a reference voltage.</p> |
