Abstract: The system and the method are used for detecting a level of liquid metal at a given location, such as a launder set between an holding furnace and a casting pit. The system comprises an emitter coil and a receiver coil in a side-by-side configuration and in close proximity of the location. In use, an AC signal is applied to the emitter coil for producing an alternating magnetic flux. At least a part of the magnetic flux passes through the location where the level of liquid metal needs to be measured and goes back into the receiver coil. The signal in the receiver coil is monitored and the data are conveyed to a control module which determines the level of liquid metal from the variation of the signal in the receiver coil. The coils of the system are advantageously provided with respective core elements having a high magnetic permeability and which are configured and disposed to channel the magnetic flux.

Abstract: Method and device for monitoring an insulating or conducting test fluid for acidity, basicity, contaminants and/or specific chemicals by monitoring the rate of modification, for example corrosion, dissolution or erosion of at least one plate of a capacitive sensor immersed in the fluid. The sensor's dielectric element is inorganic or piezoelectrically active ceramic. Capacitor plates can be different materials, foil or coated/deposited metals modified by the test fluid. Capacitance is measured over time, its change due to modification of sensor plate area is recorded and used to determine quantity of acid, alkali, contaminants and/or chemicals in the test fluid. Piezoceramic dielectric allows the detector to be vibrated. The sensor can be attached to an ultrasonic transducer. Presence of specific chemicals requires a chemically non-reactive and a chemically reactive electrode re the chemical of interest. If the test fluid is conductive, the changed capacitance is measured in an insulating fluid.

Abstract: Method for detecting changes of magnetic response with at least one magnetic particle (20) provided with an external layer (22) in a carrier fluid. The method comprises utilization of a method of measurement comprising measuring of the characteristic rotation period of said magnetic particle regarding the effect of said external layer.

Abstract: A field generator/detector including at least one super-toroidal conductor and a device to energize the super-toroidal conductor to generate varying electric and magnetic fields. Where conductor has a length l, the super-toroidal conductor is energized with at least one frequency component equal to or greater than 2c/l, where c is the speed of light in free space. Then the near field generated at this frequency close to the super-toroidal conductor has a strongly inhomogeneous spatial distribution similar or more complex than that generated by four or more electric charges and/or current loops. At any particular moment in time, the amplitudes of the electric and magnetic fields components of such a complex field change significantly over a distance comparable with the smallest winding feature of the super-toroidal conductor. The field generator/detector may be used in a sample analyzer having a chamber and a sample holder within the chamber.

Abstract: Apparatus for detection and measurement of agglutinations of magnetic particles employing Hall sensors. A low frequency AC signal is employed to excite or bias the Hall sensors which reside in a DC magnetic field. The particles are moved into operative relationship with the Hall sensors in order to generate a signal representing the number of particles on the substrate. The method for such detection and measurement is also part of the invention.

Abstract: A method and mechanism for ensuring quality control in printed biological assays is provided. A multi-ejector system having a plurality of individual drop ejectors is loaded with a variety of biofluids. Biofluids include at least a carrier fluid, a biological material to be used in the testing, and markers, such as fluorescent dyes. Data regarding the biofluid loaded in each of the drop ejectors is stored along with an expected signature output of the biofluid. Particularly, the signature output represents signals from individual ones of the fluorescent markers included within the biofluid. Once a biological assay consisting of the biofluid drops has been printed, a scanner capable of detecting the markers scans the biological assay and obtains signature output signals for each of the drops of the biological assay.

Abstract: A system and method for monitoring the composition of a magnetically permeable material, where the system comprises a first container containing a volume of magnetically permeable material; a flow path for flowing the magnetically permeable material out of the container; a sensor for determining the inductance of the magnetically permeable material; and a sensor for determining the density of the magnetically permeable material. The sensors for determining the density and inductance of the magnetically permeable material are flow connected to the flow path.

Abstract: An apparatus is provided for quantitatively measuring groups of magnetic particles. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: A magnetoinductive flowmeter incorporates a measuring tube, a magnet serving to generate a periodically alternating magnetic field that extends in a direction at least essentially perpendicular to the axis of the measuring tube, and two measuring electrodes positioned along a connecting line that extends in a direction at least essentially perpendicular to the axis of the measuring tube and to the vector of the magnetic field. An output device is provided by means of which a value for the constant-voltage component of the voltage collected at one or both of the measuring electrodes and differentiated from a reference potential is displayed to the user and/or is made available to the user for further processing. An equivalent flow-measuring process is also described.

Abstract: Apparatus for detection and measurement of agglutinations of magnetic particles employing Hall sensors. A low frequency AC signal is employed to excite or bias the Hall sensors which reside in a DC magnetic field. The particles are moved into operative relationship with the Hall sensors in order to generate a signal representing the number of particles on the substrate. The method for such detection and measurement is also part of the invention.

Abstract: A method and apparatus for retrieving magnetic casing fragments from a well using a shrouded magnet are disclosed. Retrieving casing fragments allows the determination of weight loss from the casing to assist in analyzing the integrity and the condition of the casing and to determine whether more expensive analysis is required. The shrouded magnet, that is formed by a non-magnetic container enclosing a source of magnetic field, recovers metal casing fragments by attracting them and other magnetic materials from oil and gas well fluids passing by the shrouded magnet device, which fragments are easily separated from the device by removing the source of magnetic field from the container.

Abstract: A chip-detector assembly has a housing and a probe. The probe is adapted to be coupled to the housing. The chip-detector assembly also includes a locking mechanism comprising a locking ring and a sleeve member. The locking ring is fixedly coupled the housing, and includes a plurality of elongated tangs arranged circumferentially around the ring. The sleeve member is fixedly coupled to the probe, and includes a plurality of contact surfaces that form an outer circumference of the sleeve member. The tangs engage the sleeve-member contact surfaces when the probe is coupled to the housing. The engagement of the tangs and the contact surfaces inhibits the probe from disengaging from the housing once the probe and the housing are coupled.

Abstract: An apparatus is provided for quantitatively measuring combinations of magnetic particles combined with analytes whose amount or other characteristic quality is to be determined. The magnetic particles are complexed with the analytes to be determined and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: The object is to improve an apparatus for measuring the concentration of a paramagnetic gas in a gas sample, in such a way a measurement signal with a low noise ratio is obtained. The apparatus proposed according to the invention is characterized by a modulatable magnetic field source 4, 5, 6, 7 with an air gap 3 as a measuring chamber for receiving the gas sample; a modulation source 26 for outputting a modulation signal to the magnetic field source 4, 5, 6, 7; a measuring element 8, disposed inside the air gap 3 and heated to an operating temperature, for outputting a heat flow measurement signal; a filter device 28, 29, for filtering periodic fluctuations out, caused by the modulation of the magnetic field source, from the heat flow measurement signal caused by the modulation of the magnetic field source, the amplitude of the periodic fluctuations, being a measure for the proportion of the gas in the gas sample.

Abstract: A magnetic oxygen analyzer which employes a detector comprising a magnetic pole, heat generator arranged in a non-uniform magnetic field where the intensity of a magnetic field produced by the magnetic pole varies, and a magnetic wind sensor disposed to not be affected by heat produced by the heat generator. A change in electrical resistance of the sensor, caused by change in magnetic wind strength, is detected as the oxygen concentration of a mixed gas. The magnetic wind is caused by the magnetic field produced by the magnetic pole and by heat produced by the heater and is related to the oxygen concentration of the mixed gas exposed to the analyzer. Advantageously, the analyzer of the invention provides improved signal to noise ratio, is immune to ambient temperature, and eliminates the need for precise temperature control.

Abstract: A sensor for detecting particles in a fluid including a housing having a cavity associated therewith, a magnet disposed adjacent the cavity to attract particles into the cavity, first and second coils wound around the outer surface of the cavity, the induction of the first coil being responsive to the particle accumulation within the cavity, the inductance of the second coil being responsive to the temperature of the fluid and being independent of the particle accumulation within the cavity, a first microprocessor coupled to the first and second coils for processing the signals received therefrom and for outputting signals indicative of the particle accumulation within the cavity, an rf transmitter for converting the signals received from the first microprocessor into rf signals, and an rf antenna for transmitting the processed signals to a remote location. The signals outputted from the first microprocessor are encoded with an identification code to identify and distinguish such signals.

Abstract: An apparatus is provided for quantitatively measuring groups of magnetic particles. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: An apparatus is provided for quantitatively measuring groups of magnetic particles. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetizations of the magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to at least one sensor such as sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: A method of determining the number of magnetic particles within a sample using a tuned circuit having a capacitor and a coil.

Abstract: A magnetic stripe card provides a quantitative tool for the measurement of magnetic sensitivity for fine-grained iron, iron oxide or other ferro-magnetic powders, that may be used for magnetic particle inspection and other purposes. The magnetic stripe card is encoded to establish distinct areas on the magnetic stripe. Each distinct area has a specific magnetic gradient. Ferro-magnetic powders are attracted to the gradient in proportion to the value of the gradient. A higher gradient more strongly attracts the powder. A determination of the sensitivity of the powder can be ascertained by observing the gradient with the lowest value to which the powder is attracted.

Abstract: 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.

Abstract: Apparatus for quantitatively measuring groups of magnetic particles. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: A magnetomechanical gas analyzer such a paramagnetic oxygen analyzer which has a dumbbell which is rotatably suspended in the region of action of an inhomogeneous magnetic field and around which a gas to be measured flows. The dumbbell is connected, fixed in rotation, to a mirror for deflecting a light beam. In order to damp in the analyzer all kinds of oscillations which have a negative effect on stability in the balance point, and to increase the detectability and the speed of the measurement, there are least two electrically conductive surface segments which are essentially perpendicular to one another are arranged for eddy-current damping on the dumbbell or in the mechanical gearing on the dumbbell and in the region of action of the inhomogeneous magnetic field. One of the surface segments may be the mirror.

Abstract: A gas measurement cell has a measurement element suspended to oscillate about a suspension axis in a magnetic field. A coil which oscillates with the element may have electrical signals applied to it to initiate oscillation and also provides an output whereby the frequency of oscillation can be measured.

Abstract: A fluid contamination analyzer employs one or more micro-miniature sensors which provide for a substantial reduction in sensor dimensions form prior art dimensions of approximately 2 in.×2 in. to approximately 1 mm×1 mm. The sensors are incorporated into probes for easy lubricant fluid accessibility or alternatively may be employed in an on-line analyzer residing in the fluid flow path. The sensors sense an impedance of the fluid which is a function of its contamination and communicates the impedance to analysis circuitry via either a hard-wired or RF data link. An array of sensors may also be utilized in conjunction with a magnetic field intensity gradient to obtain a particulate distribution across the array. Impedance information, which is indicative of the particulate distribution, is communicated to analysis circuitry individually or in a multiplexed format for fluid contamination analysis.

Abstract: A sensor responds to a magnetic wind produced by the magnetic susceptibility of a target component gas, such as oxygen, which is present together with a background gas in a sample located in a measurement field produced in a measurement device. A background sampler also determines thermal and physical characteristics in a conditioned flow path, and a processor performs a computational correction on the detected magnetic wind signal to more accurately determine the concentration of the target gas. The background sampler includes a mass flow cell in series with a laminar flow device to measure heat capacity and viscous properties of the sample. It derives the gas viscosity from a differential pressure measurement; and preferably determines the heat capacity and thermal conductivity of background gases, the composition of which may be unknown, to compensate for their effects on the magnetic wind sensor elements.

Abstract: A sensing device in which a high frequency signal is transmitted from an oscillator to a sensor through a transmission path, a reflection signal generated according to a variation of an impedance of the sensor sensing the presence or absence of an article is detected by a reflected wave sensor, and the presence or absence of the article is detected by the presence or absence of the reflection signal and a level of the signal, whereby the presence or absence of an article other than metal and the kind of the article can be detected regardless of whether a container holding the article is transparent or opaque.

Abstract: Method and apparatus for determining concentration of a trace of contaminant magnetic substances contained in a non-magnetic substance. A magnetic field (3) is applied to the non-magnetic substance (1) from outside a duct (2) through which the non-magnetic substance is advanced so that magnetic substances contained in the non-magnetic substance are magnetized. At a downstream in the duct, an intensity of magnetic field produced substantially only by the magnetized magnetic substance is detected by a magnetic sensor (8) having a superconducting quantum interference device (SQUID).

Abstract: The magnetic or conductive properties of a test fluid, or of particles within a test fluid, are measured by an apparatus comprising a solenoidal coil (1a), a magnetic field carrying means (23) disposed radially outside the solenoidal coil, a tubular electrostatic screen (22) disposed radially within the solenoidal coil and radially outside a sample detecting volume, the test fluid being disposed in use within the sample detecting volume and separated radially from the innermost surface of the electrostatic screen by an air gap (18). The solenoidal coil is energised in use, and sensing means is provided for sensing the impedance of the solenoidal coil.

Abstract: Apparatus for quantitatively measuring groups of magnetic particle. The particles are complexed with substances to be determined and are excited in a magnetic field. The magnetic particles are thereby caused to oscillate at the excitation frequency in the manner of a dipole to create their own fields. These fields are inductively coupled to sensing coils fabricated in a gradiometer configuration. The output signals from the sensing coils are appropriately amplified and processed to provide useful output indications.

Abstract: An apparatus for analyzing a sample of a mixture of compounds selected from the group consisting of polynucleotides, proteins and fragments thereof attached to magnetized moieties which generate a magnetic field contained on a substrate comprising:a) a support for mounting the substrate,b) a magnetic field detector mounted adjacent the substrate, the magnetic field detector generating an electrical signal in response to a magnetic field from the substrate,c) scanning means for moving the magnetic field detector relative to the substrate, andd) an amplifier operatively connected to the magnetic field detector to amplify a signal generated thereby.

Abstract: The invention relates to a micro-mechanical device for determining the oxygen content in a gas mixture or gas matrix including a dumbbell-shaped element having a base plate and two volumes of the gas to be measured arranged on opposing sides of a center portion of the base plate. The center portion of the base plate is held by a clamping band which is torsionally held such that the base plate rotates about the center portion. A mirror element on the base plate is used to determine a rotational position of the base plate and a compensation coil for conducting current and creating a rotational force to counter any rotation by the base plate is arranged on the dumbell-shaped element.

Abstract: A flow-through system for determining the particle size distribution of iron oxide particulate matter in a reactor water sample. The system includes a magnetic filter having a chamber through which a stream of reactor water. The chamber is surrounded by a winding which is coupled to an electrical circuit for generating a varying magnetic field which interacts with any magnetic particulates entrained in the water sample flowing through chamber. When a strong magnetic field is established, magnetic particles are filtered out of the water stream flowing through the chamber by magnetic attraction. Therefore, only particles which are non-magnetic or slightly magnetic pass through the magnetic filter. The particles which pass through the magnetic filter then enter a conventional particle distribution analyzer which counts and sizes the particles in the water stream flowing therethrough.

Abstract: A chip detector assembly includes a body member with a cylindrical passage for receipt of a chip detector. The chip detector includes a triangular flange which cooperates with a congruent triangular window in the housing to permit the chip detector to engage and lock to the housing in any one of three equally spaced, distinct positions.

Abstract: An acoustic monitor assembly for monitoring the particulate content of a liquid, comprising, a body having an electrically conductive portion, the body contacting a liquid whose content is to be monitored in use, a magnetic field generator for generating a magnetic field to which the electrically conductive portion of the body is exposed, the magnetic field generator being positioned such that magnetic particulates in the liquid are drawn on to said body, and a signal generator for inducing eddy currents which oscillate at an acoustic frequency in the electrically conductive portion of the body and in response to which the body is caused to vibrate, and a monitoring for observing the vibration condition of the body so as to provide an indication of the content of said particulates which are drawn onto the body in the liquid.

Abstract: A device and a method for its manufacture, for magnetic-inductive measurement of the quantity of mixture flowing through a pipeline into which the device has been incorporated. The device includes a housing having a measuring tube with an electrically insulating lining therein. The lining substantially consists of wear-resistant, insulating ceramic material in the form of tiles applied on a layer of plastic material having a thickness between 3 and 10 mm. The joints between the tiles are filled with plastic material. The housing contains magnetic coils. A pair of electrodes are mounted in the measuring tube and extend through the wall of the measuring tube and are insulated in relation to it. Within the housing, the electrodes are connected to lines leading to measuring members for measuring the voltage difference generated in the flowing medium by the magnetic field of the magnetic coils.

Abstract: A method and an apparatus for measuring the toner concentration and the amount of electric charge, capable of simultaneously measuring the toner concentration and the amount of electric charge easily and maintaining high precision using a simple device.

Abstract: Ferromagnetic tagging material is suspended in a constituent of a two constituent mixing system. Two tagging material sensors are employed that respectively monitor the tagged constituent as it flows in the system alone and the mixed constituents as they flow to a dispenser nozzle. A monitor calculates the volumetric ratio of the two constituents present when mixed based upon the concentration of tagging material sensed by each sensor. A warning is given when the calculated ratio exceeds predetermined limits.

Abstract: A magnetochemical sensor for continuous and in-situ sensing of a given chemical species/stimuli includes two magnetically-soft magnetic film layers and a chemical transduction layer that shrinks or swells in the presence of that given chemical species/stimuli. The magnetic switching characteristics of the sensor are dependent upon the thickness of the chemical transduction layer. A method for remotely interrogating the magnetic switching characteristics of the sensor is also provided. In the method, magnetic flux detecting coils are utilized to monitor the sensor.

Abstract: 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.

Abstract: A method of determining a concentration of magnetic powderly material in a sample is disclosed. In this method, a pair of series-connected exciting coils are disposed in such a manner that magnetic fields generated from the respective exciting coils oppose to each other. A detecting coil is disposed at a position where the magnetic fields from the pair of exciting coils cancel out each other. A sample mixed with magnetic powder is inserted into one of the pair of exciting coils. Then, the method detects a voltage induced in the detecting coil in association with the insertion of the sample into the exciting coil and determines the concentration of the magnetic powder in the sample based on the detected voltage.

Abstract: An apparatus and method for determining a parameter of a particle in a fluid is disclosed and, in particular, an apparatus and method for determining contamination or machine wear by the measurement of contamination or wear particles in a fluid used in the machine is disclosed. In a first embodiment, a measurement cell is provided with a fluid flow path. A first hall probe is arranged adjacent to the flow path for detecting dia-magnetic, para-magnetic, ferro-magnetic particles and a second optical sensor formed of a light emitting diode and phototransistor are provided for optically detecting the particles. A correlation between the hall probes and the optical detector enables an indication of the particles to be obtained so that a parameter of those particles can be determined to provide an indication of contamination or machine wear.

Abstract: In an electric conductivity measurement circuit according to the invention, there are provided first and second cores for forming a closed flux loop in a liquid whose electric conductivity is to be measured, a first coil is wound on the first core, and a second coil is wound on the second core in a direction opposite to the direction of the winding of the first coil, a closed circuit includes the first and second coils, a reference resistor Rr and switch means, and the switch means is periodically turned on and off to periodically incorporate the reference resistor Rr in the closed circuit, thereby calculating the electric conductivity of the liquid by comparing a voltage induced at the second coil where the reference resistor Rr is incorporated in the closed circuit, with a voltage induced at the second coil where the reference resistor Rr is not incorporated in the closed circuit.

Abstract: The invention is an apparatus for controlling an electrical heating element to control a cooking temperature of a cooking pot and contents therein.

Abstract: Apparatus for monitoring particles in fluid systems in which a detector has electrical contacts that are bridged by particles captured from suspension in the fluid. Upon detection of a particle, a control microprocessor stores a predetermined quantity of electrical energy on a capacitor, which is then discharged through an inductor to burn off the particle at the detector. The burn-off charge and return lines from the charge storage capacitor are un-grounded, and are connected by respective electronic switches through relay contacts to the conductors connected to the chip detector. The relay contacts are also connected to the inputs of a differential amplifier for detecting presence of a chip bridging the detector contacts and monitoring continuity of the conductors to and from the detector. The relay is powered by system voltage, and in the event of system power failure connects the chip detectors directly to warning lamps on an operator panel.

Abstract: A toner monitor particularly suited for monitoring toner concentration in a two-component development mixture includes an electrically conductive probe mounted in a wall of a development apparatus but the probe does not extend substantially into the developer mixture. A square wave generator or other multifrequency signal source generates a first signal so that electromagnetic energy is carried along the probe and into the mixture. A second signal is generated in response to an impedance mismatch between the mixture and the probe. In response to the second signal, a third signal is generated relating to adjustment of composition content of the development mixture.

Abstract: An object of the present invention is to provide a magnetic powder for magnetic recording and a magnetic recording medium wherein stability of a coercive force of each of the magnetic powder and the magnetic recording medium is improved.The magnetic powder for magnetic recording and the magnetic recording medium having the magnetic powder used therfor are characterized in that the magnetic powder is composed mainly of a plate-shaped ferrite having a crystalline anisotropy and containing an element effective for reducing a temperature coefficient of coercive force of the magnetic powder, and that a difference between a coercive force (Hc) of the magnetic powder at a room temperature and a coercive force (Hc(s)) of the magnetic powder in such a state that the magnetic powder is dispersively deposited on the surface of silica (SiO.sub.2) powder particles is 100 (Oe) or less.

Abstract: Apparatus for detecting ferromagnetic debris in a fluid medium in a container includes a plug attachable to the container and having an associated magnetic field preferably produced by a permanent magnet. The plug is at least partly exposed to the fluid to capture debris in the fluid. The apparatus further includes a portable sensor for optically sensing the captured debris, with the sensor having a probe that is connectable to the plug. A method for using such apparatus is provided, and in general a method of detecting ferromagnetic particles in a fluid medium in a container includes the steps of: a) magnetically capturing particles from the fluid using a plug with the container, and b) interrogating the plug with light for captured particles using a portable probe.

Abstract: Apparatus is disclosed for detecting the presence of the type of debris in a fluid system. The apparatus detects the presence of debris, measures the accumulation and identifies the specific types of the debris. A plurality of sensors, connected in a bridge detecting circuit, are assembled in the apparatus in the fluid flow, each of said sensors are tuned to a specific preselected frequency which is characteristic of one material type of the debris. A variable frequency power supply is connected to the detecting bridge for exciting the bridge. Switching means are provided external to the detecting apparatus for selecting one of said sensors as the detecting leg of the bridge. When the sensor has been selected, the bridge is excited at the resonant frequency of the selected sensor for identifying a specific material type of the debris.

Abstract: A highly accurate electromagnetic-induction-type conductivity and dielectric constant meter is obtained by using a calibration box (instrument) and a structure as below. The conductivity and dielectric constant meter employs an electromagnetic inductive probe which includes a primary transformer composed of a toroidal core with a wound primary coil, a secondary transformer composed of a toroidal core with a wound secondary coil, an electrostatic shield shielding the transformers, and cables that connect the probe to a meter. To eliminate the electrostatic capacity produced by causes other than electromagnetic induction, the structure of the probe is symmetrical. In a first embodiment, the secondary transformer is placed between two parts of the primary transformer, which has two cores of the same shape that are placed symmetrically.