Communications: electrical – Wellbore telemetering or control – With position or depth recording
Patent
1991-05-23
1992-02-25
Moskowitz, Nelson
Communications: electrical
Wellbore telemetering or control
With position or depth recording
3408571, 375 22, 324369, G01V 140
Patent
active
050917250
ABSTRACT:
A logging tool (22) for use in measuring underground parameters and transmitting electromagnetic energy (38) through the lithosphere (16) is disclosed. The logging tool (22) includes a CPU-controlled data acquisition circuit (44-56) to measure down-hole parameters. A modulator (58) generates an output signal modulated to describe the measured parameters, and the modulator drives a power amplifier (66). In the power amplifier (66), DC current from a positive terminal of a battery (30) is routed through a semiconductor switching device (74) and an inductor (78) to an electrode (34), which directly contacts a well casing (18). A ground terminal (80) couples to a negative terminal of the battery (30) and another electrode (36), which also directly contacts the well casing (18). A diode (76) couples between the switch (74) and inductor (78) at a cathode and ground (80) at an anode. A capacitor (82) couples between the electrodes (34-36). A pulse width modulator (70) controls switching of the switch (74) in response to an oscillator signal and an error signal. The error signal is supplied from an error amplifier (68) which compares the modulator output signal to the transmitted output signal. Accordingly, a feedback loop controls the duty cycle of a constant frequency switching signal applied to the switch (74) so that the transmitted signal tracks the modulator output signal.
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patent: 4837518 (1989-06-01), Gard et al.
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patent: 4891641 (1990-01-01), Gard et al.
patent: 4902981 (1990-02-01), Gard et al.
patent: 4906928 (1990-03-01), Gard
Atlantic Richfield Company
Moskowitz Nelson
LandOfFree
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