ULTRASONIC GAS FLOWMETER

To reduce a mount area and power consumption and improve the resolution of adjustment.SOLUTION: An ultrasonic gas flowmeter comprises: a passage 1 in which a gas to be measured flows; a pair of transducers 2, 3; a transmit unit 4 for causing an ultrasonic wave to be transmitted from one transducer; a receive unit 5 for amplifying an ultrasonic receive signal having been received by the other transducer; a comparison unit 8 for comparing the ultrasonic receive signal amplified by the receive unit 5 with a threshold; a time-keeping unit 9 for measuring a time duration from when the ultrasonic receive signal first rises above the threshold during level increase till when it last drops below the threshold during level decrease; and a control unit 11 for adjusting the gain set value of the receive unit 5 so that the time duration falls within a designated range.SELECTED DRAWING: Figure 1 【課題】実装面積および消費電流を低減し、調整の分解能を細かくする。【解決手段】超音波気体流量計は、測定対象の気体が流れる流路１と、１対のトランスデューサ２，３と、一方のトランスデューサから超音波を送信させる送信部４と、他方のトランスデューサで受信された超音波受信信号を増幅する受信部５と、受信部５によって増幅された超音波受信信号と閾値とを比較する比較部８と、超音波受信信号がレベル増大中に閾値を最初に過ぎて上回ったときから、レベル減少中に閾値を最後に過ぎて下回るまでの時間幅を計測する計時部９と、時間幅が予め指定された範囲内になるように受信部５のゲイン設定値を調整する制御部１１とを備える。【選択図】 図１