Electricity: measuring and testing – Of geophysical surface or subsurface in situ – With radiant energy or nonconductive-type transmitter
Patent
1995-11-28
1997-02-04
Snow, Walter E.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
With radiant energy or nonconductive-type transmitter
324233, G01V 328, G01V 318, G01R 3312, G01N 2772
Patent
active
056002467
ABSTRACT:
An apparatus for calibrating phase response of a receiver in an induction well logging instrument. The apparatus includes a source of alternating current selectively coupled to a transmitter. A low-gain antenna is disposed proximal to the transmitter for generating voltage in response to a magnetic field generated by the alternating current in the transmitter. The instrument includes a receiver spaced apart from transmitter. A phase comparator is coupled at one input to the low-gain antenna and at its other input to the source of alternating current. The phase comparator generates a signal corresponding to phase difference between the voltage in the low-gain antenna, and the alternating current. A sample and hold circuit is coupled to phase comparator for retaining the most recent signal from the phase comparator. A time-delay circuit is coupled to the source of alternating current and to the sample and hold circuit. The time-delay circuit output consists of the alternating current time-shifted by an amount corresponding to the difference in phase. A current switch is interconnected between the output of the delay line and the receiver for selectively injecting the time-shifted alternating current into the receiver. When the time-shifted alternating current is injected into the receiver, the transmitter is turned off. The receiver output and the time-shifted alternating current are coupled to analog to digital converters and a computer for determining the phase difference between the receiver output and the delayed alternating current.
REFERENCES:
patent: 4720681 (1988-01-01), Sinclair
Fanini Otto N.
Forgang Stanislav
Fagin Richard A.
Snow Walter E.
Western Atlas International Inc.
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