Method and Apparatus for Amplifying Seismic Signals (Patent No: 664610)

Inventor: Alvey, Graham C.

Location: Calgary

Comments: N/A

Description:
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. The method for controlling the amplification of a signal from a seismic detector to provided a record of said signal portions representing said signal as modified by an automatic volume control and other portions representing said signal unamplified by said automatic volume control in which the signal from the seismic detector is passed through an amplifier which has an automatic volume control connectible to it to control the amplitudes of signals sent from the amplifier to a recorder, the improvement comprising periodically disconnecting and subsequently reconnecting the automatic volume control and the amplifier at predetermined times and for predetermined time intervals while the record is being made to provide a seismic record which has preselected portions which are free from the effects of said automatic volume control interspersed between preselected portions of said record which are affected by said automatic volume control.

2. The method of amplifying a seismic detector signal having a portion of relatively large amplitude appearing subsequent to a portion of relatively small amplitude and substantially immediately followed by another portion of relatively small amplitude comprising the steps of automatically controlling the gain with which said signal is amplifier as a function of the amplitude of said signal until substantially the end of said portion of relatively large amplitude, abruptly increasing the gain with which said signal is amplified to substantially a maximum value independently of the automatic gain control during occurrence of said other portion of small amplitude, and then resuming automatic control of the amplification of said signal.



3. The method of amplifying a seismic detector signal having a first portion of relatively large amplitude appearing at the beginning of said signal and having another portion of relatively large amplitude appearing subsequent to a portion of relatively small amplitude and substantially immediately followed by another portion of relatively small amplitude comprising the steps of maintaining the gain with which said signal is amplified at a minimum value during occurrence of said first portion of relatively large amplitude, automatically controlling the gain with which said signal is amplified as a function of the amplitude of said signal until substantially the end of said other portion of large amplitude, and then abruptly increasing the gain with which said signal is amplified to a maximum value independently of the automatic gain control during occurrence of said other portion of small amplitude.

4. In the method of amplifying a seismic signal wherein a detector for seismic signals is employed and the amplification of an electric signal from said detector is automatically varied as a function of the amplitude of the signal, the improvement which comprises abruptly eliminating the automatic control of said amplification for a preselected portion of said signal to provide substantially maximum amplification of said signal during said portion, said portion occurring after a predetermined time interval has elapsed from the time said signal was initiated.

5. Apparatus for controlling the amplification of a signal from a seismic detector to provide a record of said signal containing some portions representing said signal as modified by an automatic volume control and interspersed other portions representing said signal unmodified by said automatic volume control comprising a seismic detector, an amplifier connected to said seismic detector to receive and amplify electric signals therefrom, an automatic volume control means connectible to said amplifier, means to initiate a seismic disturbance, a timing device connected to the last said means to be placed in operation when said seismic disturbance is initiated, means operated by said timing device alternately to connect said automatic volume control to said amplifier to control the amplitude of signals sent from said amplifier to a recorder and to disconnect said automatic volume control from said amplifier, and means to preset said timing device to connect and disconnect said automatic volume control and said amplifier during preselected interspersed intervals while said record is being made to provide preselected intervals of said record which are free from the effects of said automatic volume control interspersed between preselected intervals of said record which are affected by said automatic volume control.