| 摘要 |
A system for selectably electrically pulsing each of a plurality of ultrasonic transducers in a testing apparatus in rapid sequence to produce a pattern of ultrasonic energy transmitted into and subsequently received from a test piece comprises a plurality of transducer pulsing circuits, each connected to a different associated one of the transducers. Each pulsing circuit includes a silicon control rectifier connected to ground and a capacitor, connected between the rectifier and the associated transducer, that is dischargeable to pulse the associated tranducer. The rectifier is switchable to an "on" condition to rapidly discharge the capacitor to ground. The rectifier maintains the "on" condition until current conducted through it drops below a characteristic holding current and thereafter switches to an "off" condition. A two-state regulated voltage source is connected to the junction between the rectifier and the capacitor in each of the pulsing circuits to provide a proper charging source for the capacitor. The regulated voltage source is maintained in a high-impedance, voltage-source state designed to maintain an existing capacitor charge in spite of device leakage currents while maintaining a current level less than the rectifier holding current. Individual capacitors are isolated by a diode "and" network in the charging current path. A quick recharge, current-source state is established to recharge the capacitors at a controlled rate to a regulated voltage level. When the desired voltage is reached, the regulated voltage source reverts to its voltage-source state to maintain the voltage until the next such cycle of operation.
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