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Hybrid conductivity sensor

  • US 9,410,910 B1
  • Filed: 05/23/2014
  • Issued: 08/09/2016
  • Est. Priority Date: 05/23/2013
  • Status: Active Grant
First Claim
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1. A sensor for measuring electrical conductivity of a fluid containing dissolved ions, comprisinga generally cylindrical tube (57) of poorly electrically conductive material, having a first, inlet end, an intermediate portion, and a second, outlet end;

  • a first toroidal transformer (52) with winding (53) arranged around said tube, near said first end, for applying, during operation, an electromagnetic voltage field to fluid within said tube, to drive a measurement current to flow through fluid in the cylindrical tube (57);

    a first annular electrode (51A), arranged inside said tube, near said first end;

    a second annular electrode (51B), arranged inside said tube, near said second end;

    an electrical conductor (56) interconnecting said first and second electrodes, in order to maintain said electrodes at a common electrical potential with each other, and to provide a lowest-resistance path for the measurement current to flow;

    a second toroidal transformer (54) with winding (55), arranged such that the electrical conductor (56) forms a turn around the second toroidal transformer, to sense a value of current in fluid in said tube (57);

    a source of a time-varying periodic electrical signal, coupled to said first toroidal winding (53); and

    a digital computing device (68), coupled to an output of said second toroidal winding (55), configured to derive, during operation, from an output signal of said second toroidal winding, a current value representing instantaneous electrical conductivity of said fluid within said tube (57).

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