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Electromagnetic borehole flowmeter system

  • US 5,297,425 A
  • Filed: 03/23/1992
  • Issued: 03/29/1994
  • Est. Priority Date: 03/23/1992
  • Status: Expired due to Fees
First Claim
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1. A flowmeter system for determining the flow of fluid through conduit, said system comprising:

  • (a) probe means for travel within said conduit and for measuring the flow of fluid therethrough, said probe means comprising;

    (1) flowmeter transducer means for effecting a magnetic field perpendicular to the axis of said conduit;

    (2) electrodes for determining the voltage induced by said magnetic field in the flow of fluid; and

    (3) first amplifier means coupled to said electrodes and impedance matched therewith for converting the output from said electrodes to a low impedance signal;

    (b) connector means for coupling said probe means and later mentioned external circuit means over distances ranging up to about 5000 feet; and

    (c) external circuit means coupled with said probe means through said connector means for applying signals to said flowmeter transducer means and for being responsive to signals from said electrodes, said external circuit means comprising;

    (1) timing signal generator means coupled to a first power supply and having first timing means for providing a later mentioned signal sampling delay and second timing means for providing a later mentioned signal blocking pulse;

    (2) variable voltage generating means coupled to a second power supply for output of a drive signal to said flowmeter transducer means, said output synchronized with signal sampling from said electrodes and delayed therefrom for about 16×

    10-9 to about 3×

    10-3 seconds, said delay provided by said first timing means, and said second power supply electrically isolated from said first power supply;

    (3) input offset circuit means coupled to said electrodes for zeroing the signal under conditions of zero flow of fluid through said probe means;

    (4) analog switching means coupled to the output of said input offset circuit means and provided with a blocking pulse for passing to later mentioned sampling means a signal substantially free of switching transients, said blocking pulse provided by said second timing means; and

    (5) sampling means coupled to the output of said analog switching means and synchronized with said drive signal to said flowmeter transducer means for coupling the signal from said analog switching means for a full master clock period occurring immediately prior to generation of a timing signal to said first timing means, said sampling means determinative of both the negative and positive peak amplitudes coupled therethrough for converting peak-to-peak AC amplitudes to a DC signal.

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