Her Majesty the Queen in Right of Canada, as Represented by the Minister

Atomic Energy of Canada Limited

Minister of National Defence

Leigh Instruments Limited

Robert W Kempster

Douglas B George

Frank B Walton

A device to detect the presence of particles, principally metallic particles, in fluid lines. The fluid to be sampled flows through a former on which is wound a coil assembly comprising a sensor coil flanked upstream and downstream by two field coils. The former is constructed with a double wall and air gap such that pressure fluctuations in the fluid are not transmitted to the coil assembly to adversely affect the positions and readings of the coils. The field coils are driven by a high frequency signal derived from a crystal oscillator and the upstream and downstream sections are wound in opposite directions such that the magnetic field from each section is cancelled out in the plane of the sense coil. When a ferromagnetic or conductive particle passes through the winding structure, the coupling in the sense coil is disturbed as the particle first interacts with the field in the upstream section of the field coil and later with the field in the downstream section of the field coil as it passes through the Sensor Coil Assembly (SCA). A characteristic signature is generated in the sense coil which results from the vector summation of these transient imbalance signals with the steady-state signal from the opposed field coils. Analysis of the phase of this signature can be used to detect and distinguish between the presence of ferromagnetic and non-ferromagnetic conductive particles. Since ferromagnetic and non-ferromagnetic conductive particles interact with the field via permeability and eddy current effects respectively, the transient phase signature has a characteristic lag-lead or lead-lag sequence depending on the nature of the particle.

Method and apparatus for detecting particles in a fluid having coils

A device to detect the presence of particles, principally metallic particles, in fluid lines. The fluid to be sampled flows through a sensor coil which is flanked upstream and downstream by two field coils. The field coils are driven by a high frequency signal derived from a crystal oscillator and the upstream and downstream sections are wound in opposite directions such that the magnetic field from each section is cancelled out in the plane of the sense coil. When a ferromagnetic or conductive particle passes through the winding structure, the coupling in the sense coil is disturbed as the particle first interacts with the field in the upstream section of the field coil and later with the field in the downstream section of the field coil as it passes through the Sensor Coil Assembly (SCA). A characteristic signature is generated in the sense coil which results from the vector summation of these transient imbalance signals with the steady-state signal from the opposed field coils. Analysis of the phase of this signature can be used to detect and distinguish between the presence of ferromagnetic and non-ferromagnetic conductive particles. Since ferromagnetic and non-ferromagnetic conductive particles interact with the field via permeability and eddy current effects respectively, the transient phase signature has a characteristic lag-lead or lead-lag sequence depending on the nature of the particle.

Detection and discrimination between ferromagnetic and non-ferromagnetic

A method of detecting the accumulation of particulate material collected on a filter medium formed of dielectric material in a chamber having the property of a microwave waveguide or transmission line comprises the steps of exciting the chamber with a microwave signal and monitoring the transmission loss of the signal through the line to sense the effective dielectric loss factor and thereby to provide an indication of the concentration or level of particulate material accumulated on the filter medium.

Method and apparatus for detecting soot concentration in particulate trap

A power line filter having at least an inductive element and a capacitive element and a circuit network with a coil therein coupled to the inductive element. The circuit network includes a capacitive element and resistive element parallel connected and in parallel with a serially connected inductive element and coil. The coil is closely coupled with the inductive element of the power line filter.

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Ottawa, Canada

Robert W Kempster