Automatic balancing system for seismic equipment
AssigneeShell Oil Company
InventorLukas Ensing
Life of this patent
Estimating the term…
Abstract
A method and apparatus for reducing ground current interference with electrical signals representative of seismic signals, said electrical signals passing from at least one geophone to a recording system via an electric circuit including a balancing circuit coupled to ground, whereby a bridge circuit is formed which includes the geophone, the electric circuit and at least part of the recording system, and wherein the balancing circuit comprises two pairs of arms, each pair having at least one arm with variable impedance. Automatic adjustment of the variable impedance occurs based upon electrical information received by a detecting circuit for determining the variation in unbalance of the bridge circuit. Impedance adjustments may be made stepwise or continuously in alternative embodiments of the invention.
Claims29
An apparatus for reducing ground current interference with electrical signals representative of seismic wave signals passing from at least one geophone via an electric circuit to a recording system, said apparatus comprising a balancing circuit including one or more pairs of arms, each pair having at least one arm with a variable impedance;
- means for electrically connecting said balancing circuit between said electric circuit and ground potential so as to form a bridge circuit in combination with said geophone, said electric circuit and at least a part of said recording system;
- means for automatically adjusting said variable impedances of the pairs of arms of said balancing circuit;
- detecting means for detecting the variation in unbalance of said bridge circuit;
- and
- means for automatically readjusting said variable impedances of said pairs of arms when the unbalance has increased as a result of such adjusting.
Method for reducing ground current interference with electrical signals representative of seismic wave signals, said electrical signals passing from at least one geophone to a recording system via an electric circuit including a balancing circuit coupled to ground potential, whereby a bridge circuit is formed which includes the geophone, the electric circuit, and at least a part of the recording system, wherein the balancing circuit comprises one or more pairs of arms, each pair having at least one arm with a variable impedance, said method comprising:
- automatically adjusting said variable impedances of said pairs of arms in a predetermined sense;
- detecting variations in the unbalance of said bridge circuit;
- and
- automatically readjusting the variable impedances in a sense opposite to said predetermined sense if the unbalance has increased as a result of said adjusting.
An apparatus for reducing ground current interference with electrical signals representative of seismic wave signals passing from at least one geophone via an electric circuit to a recording system, said apparatus comprising:
- a balancing circuit including one or more pairs of arms, each pair having at least one arm with a variable impedance;
- means for electrically connecting said balancing circuit between said electric circuit and ground potential so as to form a bridge circuit in combination with said geophone, said electric circuit, and at least a part of said recording system;
- a detection and decision circuit for detecting a variation in the balance of said bridge circuit;
- a binary counter for adjusting each of said variable impedances and for readjusting each of said variable impedances if an increase in unbalance is detected by said detection and decision circuit after said adjustment;
- and
- clock means for causing said adjusting and readjusting of said variable impedance to occur in steps.
Dependencies are inferred from the claim text.