PROBLEM TO BE SOLVED: To reduce attenuation of a reception signal that occurs when passing through secondary winding.SOLUTION: Primary windings N1A and N1B, primary windings N2A and N2B, and primary windings N3A and N3B are wound around three poles respectively, and a secondary winding NT and a shunt winding NS are wound around another pole. An ultrasonic vibrator 1 is connected to one end of the secondary winding NT and a processing system containing a preamplifier 4 or the like is connected to the other end. Switches Q1 and Q2, Q3 and Q4, and Q5 and Q6 are provided to turn on/off energizing of current to the primary windings N1A and N1B, primary windings N2A and N2B, and primary windings N3A and N3B respectively. Switches Q7 and Q8 are provided to form a first state in which the shunt winding NS is grounded and a second state in which the shunt winding is not grounded. A transmission waveform forming circuit 3 controls the switches Q1-Q6 during a transmitting period by using a pattern corresponding to a desired ultrasonic waveform, and controls the switches Q7 and Q8 to be in the first state during the transmitting period and to be in the second state at least during a period of time including a receiving period within a time period except the transmitting period.COPYRIGHT: (C)2009,JPO&INPIT【課題】 2次巻線を通過する際の受信信号の減衰を減らす。【解決手段】 3つのポールに、それぞれ1次巻線N1A,N1B、1次巻線N2A,N2Bおよび1次巻線N3A,N3Bを巻き、1つのポールに2次巻線NTとシャント巻線NSとを巻く。2次巻線NTの一端に超音波振動子1を、他端に前置増幅器4などからなる処理系をそれぞれ接続する。1次巻線N1A,N1B、N2A,N2BおよびN3A,N3Bへの通電をそれぞれオン/オフするために、スイッチQ1,Q2、Q3,Q4およびQ5,Q6を設ける。シャント巻線NSを接地する第1の状態および接地しない第2の状態を形成するために、スイッチQ7,Q8を設ける。送信波形生成回路3は、送信期間に所望超音波波形に応じたパターンでスイッチQ1~Q6を制御し、送信期間には第1の状態となり、送信期間以外の期間のうちで少なくとも受信期間を含む期間に第2の状態となるようにスイッチQ7,Q8を制御する。【選択図】 図1
