Development of Borehole Ultrasonic Measurement System

We developed borehole ultrasonic measurement system which can measure the volume of a cavity passed through by the borehole. The system consists of PXI, a digital oscilloscope, the high voltage pulse generator, transmitting and receiving piezoelectric sensors, the electronic compasses and a rotational motor. Transmitter and receiver sensors have main frequency of 20 kHz and radial directivity, and the very small two electronic compasses are installed for measuring azimuth angle of the reflection event. It is found that beam width of the transmitter sensor is more than 90 º, which means that the signal can be detected although the reflector of the cavity has steep angle to the direction of the propagation of the ultra sonic wave. To verify the feasibility of the system, the experiments were conducted at the water tank. The distances which were measured from the reflection events were coincident with real distance.