| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a gas sensor capable of measuring the evaporated fuel concentration in purge gas and a purge gas flow rate by a single sensor, and a measuring method using the sensor. SOLUTION: Gas concentration measurement is executed as follows. A received wave transmitted by an ultrasonic element 35 and received is reshaped and integrated by an integration circuit 67, and a peak value is retained by a peak hold circuit 69. A determination value is set by a resistance voltage- dividing circuit 71 based on the peak value, and the time when the integrated value of the received wave is determined to reach the set value by a comparator 73 is defined as an arrival time. The gas concentration is detected based on the period from the transmission time to the arrival time. Gas flow measurement is executed by controlling a thermistor 48 at a fixed temperature by a flow measuring circuit 76, and by detecting a voltage applied on the thermistor 48 as a signal value showing the gas flow rate.</p> |
