1. Prüftechnik Dieter Busch AG

US 7,956,601 B2 (7956601)

Device and process for Detecting Particles in a flowing liquid (2007)

Summary: Frequency-selective filtering of eddy current signals.

A process and device for detecting electrically conductive particles in a liquid flowing in a pipe section, the liquid being exposed to periodic alternating electromagnetic fields by a transmitter coil which induces eddy currents in the particles, a probe made as a coil arrangement and which has an effective width producing a periodic electrical signal based on the eddy currents. The signal ha a carrier oscillation with an amplitude and/or phase which is modulated by particles passing across the effective width of the coil arrangement, the probe signal being filtered by a frequency-selective first filter unit, the filtered signal being sampled by a triggerable A/D converter stage to obtain a demodulated digital measurement signal, the digital measurement signal being filtered by a digital, frequency-selective adjustable second filter unit to obtain a useful signal, and the useful signal being evaluated to detect passage of electrically conductive particles in the pipe section.

2. United Technologies Corporation

EP 3,171,168 B1 (3171168)

Monitoring System for Non-Ferrous Metal Particles (2016)

Summary: Inductive bypass sensing of non-ferrous debris.

This debris monitoring system detects non-ferrous metal particles within the lubrication flow of a gas turbine engine geared architecture. The system utilizes an inductive sensor comprising field and sense coils to identify metallic debris based on predefined signal profiles. To improve accuracy, a magnetic device diverts ferrous particles away from a dedicated bypass conduit where the inductive sensing occurs. This allows for the early detection of wear in components like journal pins coated with copper, silver, or lead.

3. United Technologies Corporation

US 5,041,856 A (5041856)

In-line metallic debris particle detection probe and resonant evaluation system utilizing the same (1988)

Summary: Early inductive non-ferrous debris monitor.

An arrangement for detecting metallic particles carried by a fluid includes a metallic probe member which surrounds an elongated passage through which the fluid flows and which is constituted by a split tube having two marginal portions delimiting a gap which extends along said passage and completely separates the marginal portions from one another. Capacitors are arranged at the gap and alternating electric current is caused to flow in the probe member around the passage so that the probe member and the capacitors form a tank circuit having resonance characteristics that are influenced by any inclusion then present in the passage in a manner dependent on the electromagnetic properties of the inclusion. The character of any metallic particle then present in the passage is determined from variations in the alternating electric current that reflect the influence of such metallic particle on the resonance characteristics.

4. United Technologies Corporation

US 10,648,361 B2 (10648361)

Oil debris monitor with sequential coil system and associated algorithms for particle confirmation (2016)

Summary: Sequential inductive coils for particle confirmation.

A debris monitoring system has a first sensor configured to generate a first signal indicating a presence of a metallic particle in a lubrication system. A second sensor is configured to generate a second signal indicating the presence of a metallic particle in the lubrication system. A signal processor is configured to determine a presence of a metallic particle in a fluid passage based on a comparison of at least the first signal and the second signal; the second signal being used to verify accuracy of the first signal. A gas turbine engine and a method for monitoring a fluid passage for debris are also disclosed.

5. Smiths Industries

US 5,485,083 A (5485083)

Transformer coupled in-line metallic debris sensor (1993)

Summary: Transformer-coupled inductive probe.

A system for sensing metallic debris in fluid flow, including an inductive probe utilizing one or more capacitors with a single turn resonant coil disposed about the flow passageway wherein a second, co-linear, multiple turn coil is provided about the passageway and loosely coupled via mutual inductance to the resonant coil such that the two windings produce a step-up transformer with increased impedance to closely match the impedance of the electrical output cable. This impedance matching reduces output signal loss permitting the sensitive components of the system to be remotely located from the usually hostile environment of the probe. Additionally, a toroid element of low loss, low reluctance material is disposed between the probe and its conductive housing to provide a guiding path for the magnetic "lines of force" of the sensing field produced by the probe, to avoid losses in the housing.

6. University of Edinburgh

US 5,811,664 A (5811664)

Debris monitoring (1995)

Summary: Capacitively shielded inductive coil.

A sensor for use in machine wear debris monitoring transducers which detect metallic particles present in a flow of fluid, such as lubricating oil. The sensor comprises an inductive coil having a plurality of turns for surrounding a non-magnetic conduit. An electrically conducting screen is located between the coil and the flow of fluid, the coil being electrically insulated from the screen, so as to isolate capacitatively the contents of the conduit from the coil. The resonant frequency of a tank circuit incorporating the sensor is thus unaffected by changes in the dielectric properties of the contents of the conduit caused by air bubbles and/or water droplets in the flow of fluid. The screen may be a single turn of thin metal foil having a gap between adjacent ends, or a mesh, or a metallic coating sprayed onto the conduit.

7. Dana Italia SRL

US 12,216,084 B2 (12216084)

Metal Debris Sensor For Oil With Temperature Compensation (2022)

Summary: Differential inductor bridge for temperature compensation.

Methods and systems are provided for an oil sensor. In one example, the oil sensor is a system for metallic debris detection, comprising a detection circuit including a first inductor and a second inductor, the second inductor shielded from the external environment, wherein the detection circuit generates an output based on a difference between a first voltage of the first inductor and a second voltage of the second inductor, where the difference indicates a presence of metallic debris within oil.

8. RTX Corporation

US 12,085,556 B2 (12085556)

Multi-Passage Oil Debris Monitor (2019)

Summary: Multi-passage inductive coil architecture.

An oil debris monitoring sensor includes a multiple of passages within the housing, each of the multiple of passages surrounded by a set of coils to detect a particle. A method for determining a presence of a particle in a system includes a) installing a single sensor in-line with an oil flow path; b) communicating oil through a multiple of passages within the housing of the single sensor; c) detecting a particle through the single sensor; and d) isolating the particle to one of the multiple of passages within the sensor housing.

9. Product Resources, Inc.

US 5,001,424 A (5001424)

In-line metallic debris particle detection probe and resonant evaluation system utilizing the same (1989)

Summary: Resonant inductive tank-circuit probe.

An arrangement for detecting metallic particles carried by a fluid includes a metallic probe member which surrounds an elongated passage through which the fluid flows and which is constituted by a split tube having two marginal portions delimiting a gap which extends along said passage and completely separates the marginal portions from one another. Capacitors are arranged at the gap and alternating electric current is caused to flow in the probe member around the passage so that the probe member and the capacitors form a tank circuit having resonance characteristics that are influenced by any inclusion then present in the passage in a manner dependent on the electromagnetic properties of the inclusion. The character of any metallic particle then present in the passage is determined from variations in the alternating electric current that reflect the influence of such metallic particle on the resonance characteristics.

10. Caterpillar Inc.

US 6,297,626 B1 (6297626)

Fluid particle sensor apparatus and method for detecting ferrous and non-ferrous metals (1998)

Summary: Hybrid magnetic capture and eddy current discrimination.

A sensor apparatus for detecting both ferrous and non-ferrous particles in a fluid including a housing adapted for insertion into a fluid line, the housing having a collection cavity formed therewithin for trapping and holding metallic particles which are suspended in the fluid as the fluid passes through the sensor. A first coil wound below the collection cavity and a second coil wound about the collection cavity, the inductance of the first coil being responsive to the temperature of the fluid passing through the sensor and the inductance of the second coil being responsive to the ferrous and non-ferrous particle accumulation within the collection cavity. An electromagnetic coil is spaced above the second coil to attract ferrous particles away from the vicinity of the second coil. Based upon eddy current principles and because eddy currents are a function of material conductivity, a first energization of the second coil generates a signal indicative of the total ferrous and non-ferrous particle accumulation within the collection cavity and a second energization of the second coil with the electromagnetic coil likewise energized generates a signal indicative of just the non-ferrous particle accumulation within the collection cavity. A microprocessor coupled to the coils calculates the percentage of ferrous and non-ferrous particles in the collection cavity and outputs such information for diagnostic, prognostic and trend analysis purposes.

11. United Technologies Corporation

US 10,409,275 B2 (10409275)

Oil debris monitoring (ODM) with adaptive learning (2016)

Summary: Adaptive learning improves oil debris monitoring accuracy.

A system and method for debris particle detection with adaptive learning are provided. The method includes receiving oil debris monitoring (ODM) sensor data from an oil debris monitor sensor and fleet data from a database, detecting a feature in the ODM sensor data, generating an anomaly detection signal based on detecting an anomaly by comparing the feature in the ODM sensor data to a limit defined by system information stored in the fleet data, selecting a maintenance action request based on the anomaly detection signal, and adjusting one or more of the feature, the anomaly, the limit, and the maintenance action request by applying an adaptive learning algorithm that uses the ODM sensor data, fleet data, and feedback from field maintenance of one or more engines that evolves over time.

12. Caterpillar Inc.

US 5,502,378 A (5502378)

Fluid particle sensor including a container, a first coil and a second coil disposed about a magnet located adjacent the container for attracting the particles (1994)

Summary: Dual-coil magnet cavity with temperature compensation.

In one aspect of the present invention, a sensor detects particles within a fluid. The sensor includes a housing that defines a cavity. A magnet is disposed adjacent the cavity bottom to attract particles into the cavity. A first coil is wound about the outer surface of the cavity. The induction of the first coil is responsive to the particle accumulation within the cavity. A second coil is wound about the magnet. The induction of the second coil is responsive to the temperature of the fluid and independent to the particle accumulation within the cavity.

13. Komatsu Ltd.

US 5,457,396 A (5457396)

Electrode Structure of Metallic Particle Detecting Sensor (1992)

Summary: Interdigitated thin-film electrodes.

An electrode structure of a metallic particle detecting sensor capable of detecting with high efficiency metal powders floating in a wide range in an oil tank. The electrode structure is formed by opposing, on a substrate, a pair of electrodes (1, 2), formed of thin film metals of such as Ta, W, Pt, Cr, Au or the like, having combed (toothed) structures with their respective teeth being meshed or interdigitated with each other.

14. The University of Akron

US 8,522,604 B2 (8522604)

Metal wear detection apparatus and method employing microfluidic electronic device (2009)

Summary: Microfluidic capacitive wear detection.

An apparatus and a method for detection of wear particles in a lubricant are disclosed. The apparatus includes a microfluidic device including a microchannel sized for a lubricant containing wear particles to pass therethrough and first and second electrodes extending into the microchannel. A detection system is coupled with the electrodes for detection of wear particles passing through the microchannel, based on a change in capacitance of the electrodes.

15. Emerson Electric Co (Computational Systems, Inc.)

US 5,262,732 A (5262732)

Oil monitor with magnetic field (1991)

Summary: Capacitive oil degradation with magnetic bias.

An apparatus for detecting the degree of deterioration in lubricating oil including a grid-like capacitive sensor, that uses the lubricating oil as a dielectric medium, and a magnetic field imposed upon the oil to attract ferromagnetic wear particles into the vicinity of the sensor. Preferably, the magnetic field is generated by a permanent magnet and an electromagnetic aligned such that the magnetic field produced by each magnet acts upon the oil along the same axis.

16. Airbus Helicopter

US 11,435,029 B2 (11435029)

Magnetic Device for Capturing Metal Wear Particles in Suspension in a Lubricating Fluid (2019)

Summary: Plug-style magnet with a presence-detector at the tip.

A magnetic device for capturing metal wear particles in suspension in a lubrication fluid, the magnetic device being for inserting in a straight-line insertion direction of the magnetic device into a wall of a casing via a through orifice serving to put an inside volume of the casing containing the lubrication fluid into communication with an outside volume outside the casing, the magnetic device presenting a longitudinal axis X, the longitudinal axis X being for putting into coincidence with the direction for inserting the magnetic device into the casing, the magnetic device comprising a permanent magnet suitable for attracting the metal particles and a presence-detector member for detecting the metal particles attracted by the permanent magnet.

17. KasperAero

Null Zone Magnetic Sensor (2025) Patent Pending

Summary: Magnetic field distortion sensing.

The Null Zone Magnetic Sensor (NZMS) is a novel sensing principle that uses a patent-pending, precisely arranged set of components to create a region with a specially shaped magnetic field. By placing a magnetic field sensor within this region, the device becomes highly sensitive to disturbances in the surrounding magnetic field. The NZMS can detect extremely fine ferrous debris, outperforming other sensors in this category. It is designed for cost-effective, high-volume production while maintaining the reliability, linearity, and sensitivity required for demanding applications. Owing to the underlying physics of its design, the NZMS remains largely unaffected by temperature variations, independent of permanent magnet composition. This characteristic provides exceptional reliability in harsh operating environments and results in inherent stability compared to other debris detection technologies. For the KasperAero design team, this stability enables greater flexibility when tailoring sensors to specific applications. The KasperAero NZMS can increase debris capture efficiency without requiring significant system redesign and can be configured to provide either an analog output or a digital signal.

18. Poseidon Systems (Impact Technologies)

US 8,274,287 B2 (8274287)

Metallic debris detection sensor (2007)

Summary: Magnetic field distortion sensing.

The present invention relates to a sensor arrangement. In particular, a sensor for the measurement of magnetically active or ferrous debris, for example, as generated as a result of machine wear. There is provided a sensor (5) having a magnetic sensor head adapted to produce a magnetic field, —a magnetic field sensor (10) responsive to changes in the magnetic field; a temperature probe (15); and processing means (50) for determining the amount of debris accumulated on the magnetic sensor head based on both magnetic field and temperature data.

19. Poseidon Systems (Impact Technologies)

US 11,300,106 B2 (11300106)

System and method for utilizing wear debris sensor to reduce damage and extend remaining useful life of gearboxes (2019)

Summary: Control actions driven by debris sensing.

A system and method employing wear debris sensors to monitor the operation of a lubricated mechanical system such as a gearbox (e.g., in a wind turbine), a transmission or an engine in order to control operation of the gearbox in order to reduce damage and/or extend the useful life of the gearbox.

20. Tecalemit Electronics Limited

EP 0116468 (0116468)

Magnetic particle collector (1984)

Summary: Retractable magnetic collector with Hall sensing.

A magnetic particle collector for magnetically attracting particles from a lubricating or other fluid has a permanent magnet in a housing of non-magnetic material which is retractable from an active position where it attracts particles to the outside of the housing to an inactive position which permits particles attracted to the outside of the housing to be flushed away by the fluid flow. The collector has a means such as a Hall effect device or a magnetic field sensitive resistor for sensing the amount of particles attracted to the housing by responding to the distortion of the magnetic field due to the accumulation of particles.

21. Caterpillar Inc.

US 5,179,346 A (5179346)

Conductive particle sensor using a magnet (1991)

Summary: Conductive particle resistance measurement.

An apparatus is adapted to detect particles within a fluid. The apparatus includes first and second electrodes within a housing. The first and second electrodes form a "V" shaped recess. A magnet is positioned within the housing to attract ferrous particles into the recess. The resistance between the first and second electrodes is measured as an indication of particles within the fluid.

22. Pratt & Whitney Canada Corp.

US 10,705,038 B2 (10705038)

Systems and methods for detecting chips in fluid of aircraft engine (2016)

Summary: Resistance across magnetic gap.

There is described herein methods and systems for detecting of metallic chips in a fluid system of an aircraft engine. A resistance value is measured across a magnetic chip detector mounted to a fluid system of the aircraft engine. The resistance value is transmitted to an engine computer of the aircraft engine. In the engine computer, The resistance value is compared to a first threshold and a first warning indicative of a chip in the fluid is issued when the resistance value exceeds the first threshold.

23. Benz Companies, Inc.

US 5,406,208 A (5406208)

Method and apparatus for eliminating chips in a chip detection circuit and for determining chip size (1993)

Summary: Energy pulsing to classify captured chips.

A chip detector is an open circuit device that attract metal chips circulating throughout a piece of equipment such as a transmission. If a chip closes the circuit in the chip detector, then it is subjected to a first pulse of energy in an attempt to burn or displace it from the chip detector contacts. The energy content of the first pulse is selected to burn fuzz, which represents chips of an acceptable size. If the chip remains in the chip detector, then it is subjected to one or more additional pulses each having a greater energy content than the first pulse. The number of pulses and their energy contents are recorded to determine the size of the chips captured by the chip detector and to provide a history of the equipment being monitored. If the chip in the chip detector exceeds a predetermined threshold, then an indication is given on a user interface.

24. Simmonds Precision Products, Inc.

US 5,214,377 A (5214377)

Magnetic debris monitor using magneto-optic sending (1992)

Summary: Magneto-optic real-time debris sensing.

A system and method for real-time detection of magnetic debris in a fluid medium utilizing the Faraday Effect. The apparatus comprises a magneto-optic sensor configured to monitor variations in a magnetic field caused by the accumulation of ferrous particles. Modulations in the magnetic field are converted into optical signals through the rotation of polarized light, providing quantitative data regarding both the total mass and the rate of debris accumulation. This optical configuration ensures immunity to electromagnetic interference and enables early identification of component wear within high-performance engine architectures.

25. Simmonds Precision Products, Inc.

US 5,675,249 A (5675249)

Portable optical fluid debris detector including cover and calibrating magnet (1994)

Summary: Portable magneto-optic debris detector.

An apparatus for detecting ferromagnetic debris in a fluid medium utilizing a magneto-optic sensor. The system includes a magnetic field probe configured to capture entrained particles from a lubricant flow, thereby modulating an electromagnetic field in proportion to the debris accumulation. A magneto-optic sensor detects these field variations and translates them into modulated light signals to determine particle quantity, mass, and accumulation rate. The device is configured for portable, nonintrusive operation, providing immunity to electromagnetic interference and enabling real-time monitoring of engine performance without the application of electrical energy in proximity to the fluid medium.

26. Rolls Royce Corporation

US 10,180,075 B1 (10180075)

On-wing component wear analysis with fluid quality sensing (2017)

Summary: Laser-excited tracer spectroscopy.

Technologies for engine fluid quality monitoring are disclosed herein. An engine system includes a gas turbine engine having one or more mechanical components, a fluid quality sensing system, and an engine controller. Each mechanical component includes a tracer material embedded in the mechanical component during manufacture. The fluid quality sensing system applies a laser beam to debris captured in an engine fluid of the gas turbine engine and detects a light signature generated by tracer material in the debris in response to application of the laser beam. The engine controller identifies the tracer material as a function of the light signature. The engine controller determines a potential wear state of a mechanical component as a function of the tracer material. The engine controller may select the mechanical component from multiple mechanical components based on the tracer material. Each mechanical component has a predetermined association with a corresponding tracer material.

27. Hitatchi Ltd.

US 5,880,835 A (5880835)

Apparatus for investigating particles in a fluid, and a method of operation thereof (1996)

Summary: Flow-cell particle imaging with CCD.

In order to investigate particles in a fluid, a flow cell causes the fluid to flow past a sensor which receives light from a continuous light emission system. When the sensor detects a change in light, a particle detector is triggered, which in turn triggers a pulse generator and hence an intermittent light emission system. Light then illuminates the flow cell to allow a CCD camera to photograph the particle. The photographs taken by the CCD camera are analyzed by an image processor. In order to obtain an accurate particle concentration measurement, it is necessary to modify the initial concentration measurement derived from the analysis of particle images by the image processor by a compensation coefficient. This operation is carried out by a concentration compensator. The result may then be displayed. Additional analysis may be carried out by changing the magnification of the CCD camera, or by selecting for analysis only those particles of a selected size or type.

28. General Electric Company

US 7,299,683 B2 (7299683)

METAL PARTICLE SENSOR SYSTEM (2006)

Summary: Combining inductive particle detection with pressure drop analysis.

A metal particle sensor system for detecting metal particles in an oil line. The metal particle sensor system may include a metal particle sensor positioned about the line, an orifice positioned within the line and downstream of the metal particle sensor, a first pressure sensor positioned upstream of the orifice, and a second pressure sensor positioned downstream of the orifice. The metal particle sensor detects metal particles in the line while the first pressure sensor and the second pressure sensor determine a pressure drop across the orifice.

29. Meggitt (Orange County), Inc.

US 8,746,045 B2 (8746045)

System and method for identifying fluids and monitoring fluid quality in a vessel (2011)

Summary: Time-domain reflectometry for fluid quality.

Methods and systems are disclosed for using time domain reflectometry to determine the identity of a fluid in a vessel, and to determine whether the quality of a fluid in a vessel is within acceptable parameters. Methods include identifying a fluid by comparing a derived characteristic of a fluid to a reference characteristic, determining the quality of a fluid by determining if a derived characteristic is within an acceptable quality range, monitoring a fluid for a dynamic change in quality or state, and identifying a fluid by comparing a transition reflection waveform to a reference signature transition. The methods are implemented in systems for identifying a fluid layer in a vessel, such as fuel, free liquid water or ice, detecting misfueling or fuel contamination, and detecting fluid state changes, such as the formation of ice.