Apparatus for measuring magnetic particles suspended in a fluid based on fluctuations in an induced voltage

DETAILED DESCRIPTION The invention generally features an apparatus for detecting magnetic particles suspended in a liquid, the apparatus comprising: a source of an electrical signal; a first coil connected to the electrical signal source; a second coil coupled to the first coil such that the first coil induces a voltage in the second coil, the second coil having an output; a conduit for passing the liquid through the region coupling the first and second coils; and an electrical signal processor connected to the output of the second coil; wherein the electrical signal processor indicates the presence of magnetic particles in the liquid based on the induced voltage.
In a first embodiment of the invention, the apparatus includes a third coil coupled to the second coil, the third coil also being connected to the electrical signal source such that the third coil also induces a voltage in the second coil.
The electrical signal processor will process the voltage induced by both the first coil and the second coil.
The first and third coils are preferably connected together in series.
The conduit includes a non permeable tube with each of the coils being wound around the tube such that a liquid passes through the center of each coil.
In the first embodiment, the first and third coils are wound around the tube in opposite directions.
In a second embodiment of the invention, the third coil is connected in series to the second coil and coupled to the first coil such that the first coil induces a voltage in both the second coil and the third coil.
In this embodiment, the second and third coils are wrapped around the tube in opposite directions.
The electrical signal processor processes the voltage across both the second coil and the third coil to detect magnetic particles.
In the first embodiment, the voltage induced in the second coil by the first coil is out of phase with the voltage induced in the second coil by the third coil.
In the second embodiment, the voltage induced in the second coil is out of phase with the voltage induced in the third coil