Posted on Apr 5, 2012 7778
This submersible sonar positioning apparatus generally consists of dual-opposed ultrasonic transducers, alternately excited, with return signals processed and displayed for observation and measurement. Typical transmitter frequencies range from 50 to 200J
The input to the transducer/switch is transformer Tl which provides isolation and impedance matching. The tum ratio of the secondary windings depends on the peak-to-peak amplitude of the transmitter output into the specified load. The transmitted pulse that appears on the secondary winding charges capacitors Cl and C2 through bridge rectifiers Dl and D3. Zener diodes D2 and D4 limit the TMOS gate bias to 12 V; Rl and R2 limit the discharge current from Cl and C2. The square-wave control input is applied to opto-isolators Ul and U2 through resistors R3 and R4. If the control input is 0 V, Ul is activated; when it changes to +5 V, U2 is activated. When Ul is activated, it saturates and reduces the gate bias to zero, turning Ql and Q2 off. Q3 and Q4 remain on, effectively shunting transducer Z2. When U2 is activated, it saturates and reduces the bias to zero, turning Q3 and Q4 off. Ql and Q2 remain on, effectively shunting transducer Zl.