Abstract: An improved well logging technique is provided for more accurately deriving measurements of sub-surface earth formations, for processing and recording such measurements to record them in reproducible form, and to more informatively display such measurements. Other significant features and aspects of the overall technique include improved methods and apparatus for deriving such measurements in digital form and for merging or combining two or more such measurements in one storage.In a particular embodiment of the invention, the logging sonde is provided with means for forming the logging data into discrete "frames" of data expressed in digital form, and for delivering such frames of data to the surface preferably in response to a command signal which is generated at the surface in correlation with the depth of the sonde in the borehole.

Abstract: In order to prevent late arriving and higher amplitude shear waves from saturating the subsurface amplifier, the amplitude of each succeeding positive half cycle of the earlier arriving compressional wave is measured and a negative feedback is supplied to the amplifier if the measured amplitude exceeds 50% of full scale. Circuitry is provided for utilization of a two transmitter, two receiver system using the same type of negative feedback to control the gain of the subsurface amplifier.