Abstract: There is disclosed a methodology for measuring the magnetic field strengths of fundamental and harmonic frequencies associated with a.c. electrical current flows over a protracted period of time; and, particularly, in hostile environments. A preferable application calls for the determination of the field strengths associated with electrical currents flowing in a.c. power, distribution lines of utilities. The monitoring instrument is positioned in relation to the power lines to be monitored, typically at the base of a pole immediately adjacent the pole of the power line or on a power line supporting pole itself. In order to provide for long term, powering of the monitoring device, d.c. power is developed utilizing the a.c. power that is present. The conversion from a.c. to d.c. is effected at a distance sufficiently far from the monitoring instrument so as not to have any consequence on the readings that are being taken.

Abstract: A current sensor includes a current carrying bus bar configured to define a pair of electrically parallel current carrying paths each having a different cross-sectional area. A sensing device is associated with each of the current carrying paths. One of the sensing devices is associated with a smaller of the current carrying paths and is sensitive to current flow through the bus bar below a threshold level. The other sensing device is associated with a larger of the current carrying paths and is sensitive to current flow through the bus bar above the threshold level. The sensing devices generate output upon detection of current flow through the bus bar. Sensor signal processing means is responsive to the sensing devices and generates output proportional to current flow through the bus bar.

Abstract: A self-excited microelectromechanical device is described. The device includes a resonating structure, such as a cantilever, which responds to a physical phenomenon by generating an induced variable frequency voltage signal corresponding to the physical phenomenon. Self-excitation circuitry connected to the cantilever processes the induced variable frequency voltage signal and produces a variable frequency voltage signal in a resonant pass band of interest that is applied to the cantilever to augment the effect of the physical phenomenon on the cantilever. An exemplary use of the device is as a power line sensor. In this context, the cantilever responds to the electric field associated with a power signal on a power line. The cantilever transforms the voltage signal of the electric field into a corresponding frequency signal. The noise-immune frequency signal can be readily processed to reconstruct the power signals carried by the power line.

Abstract: An improved method and apparatus for detecting signals on a twisted pair of transmission lines includes a sensor for nonintrusively coupling a portion of the signal to the apparatus. A filter is coupled to the sensor and filters unwanted frequencies from the signal. The signal is then amplified and optionally passed to an identification circuit which identifies the presence of high and low frequency signals. The signal is rectified creating a DC signal proportional to the detected signal's strength. An audio tone proportional to signal strength is generated and the tone is amplified and output.

Abstract: An alternating current in a conductor is measured using a Faraday element. The Faraday element is disposed around the conductor and linearly polarized light is supplied to the device. The plane of polarization of the linearly polarized light is rotated through a measuring angle in the Faraday element. This light is divided into two light signals having planes of polarization at right angles to each other. The two light signals are converted into corresponding electrical signals by optoelectric converters. These electric signals are split into their direct signal components and their alternating signal components. The quotients of the difference and sum of the alternating signal components as well as the quotient of the difference and sum of the direct signal components are calculated. A temperature-compensated measuring signal is derived from these calculated quotients.

Abstract: The dynamic range of a current transformer (CT) is increased without reducing the scaling of measurements at the low end of the dynamic range by designing the core of the CT to saturate only after about 90 electrical degrees of the maximum current to be measured. The measurements taken during this first 90 electrical degrees before the core saturates are doubled to in effect add measurements representing the mirror image of the first 90 electrical degrees. Timing of the digitized samples taken during the first 90 electrical degrees is adjusted to account for core reset energy errors, by determining the rate of change of current just after a zero crossing and selecting an empirically determined value of current for timing the start of the measurement samples.

Abstract: An apparatus for measuring an a.c. current flowing in an electric cable comprises a pair of jaws for receiving the cable and which are movable towards one another to engage the opposite sides of the cable. A potentiometer generates a signal ("cable size signal") corresponding to the relative positions of the jaws. A set of coils is provided adjacent the jaws to detect the magnetic field generated by current flowing in the cable. A circuit in the housing is responsive to the cable size signal and the voltage induced in the coil for determining the amplitude of the current flowing in the cable and displaying the same on a display.

Abstract: An alternating current sensor includes a first conductor plate, a second conductor plate positioned in spaced relationship relative to the first conductor plate and facing the first conductor plate, and a third conductor plate for electrically interconnecting the first and second conductor plates to form a connected conductive path along the first and second conductor plates. The first and second conductor plates are shaped to form respective magnetic field constituents around each of the first and second conductor plates during current flow along the conductive path. A sensor, made up of one or more air-core coils, is provided for sensing changes in magnetic flux within a predetermined region, such as in a passage between the first and second conductor plates and/or near respective outer surfaces of the first and second conductor plates.

Abstract: An optical voltage/electric field sensor includes a crystal having a refractive index distribution which depends on an electric field applied thereto, wires for leading the electric field onto the surface of the crystal, a detector to detect changes in the refractive index distribution, and a transparent material having a low extinction coefficient and dielectric constant surrounding the crystal. Such a sensor is particularly useful for measuring the voltage of high frequency dryers.

Abstract: A magneto-optical element is of a rare-earth iron garnet crystal expressed at least by formula 1, and a element in whose composition range the value of X is set at 0.8.ltoreq.X.ltoreq.1.3; that of Y at 0.2.ltoreq.Y.ltoreq.0.4; that of Z at 0.1.ltoreq.Z.ltoreq.0.9; and that of W at 0.ltoreq.W.ltoreq.0.3; and R element is made at least one or more kinds of rare-earth elements. An optical magnetic field sensor is composed in such a manner that light diffracted by magnetic domain structure of rare-earth iron garnet crystal can be detected up to a higher-order light by optical fiber on light output side through optical system arrangement. A magnetic field measuring equipment composed of the optical magnetic field sensor has a linearity error of .+-.1.0% or less within a magnetic field range 5.0 Oe to 200 Oe, and allows a measuring accuracy higher than with prior art equipment.(Bi.sub.X Gd.sub.Y R.sub.Z Y.sub.3-X-Y-Z)(Fe.sub.5-W Ga.sub.W)O.sub.

Abstract: In an optical unit (a), a first polarizer, a first light wave phase modulator (a Pockels device), a second light wave phase modulator, and a second polarizer are arranged in this sequence. A voltage to be measured is applied to the first light wave phase modulator. A control modulation voltage which has a frequency higher than that of the voltage to be measured is applied to the second light wave phase modulator. A signal processing unit (b) consists of: an O/E converter which converts the intensity of light output from the optical unit (a) into an electric signal; a phase shifter which shifts the phase of the control modulation voltage applied to the second light wave phase modulator by .pi./2 radians; an adder 16 which adds an output of the O/E converter 17 to that of the phase shifter 15; and a demodulator c which demodulates output of the adder 16.

Abstract: A direct current of high intensity having alternating current components superposed thereon is flowing in a conductor 1 through a magnetic circuit 5, 6. Two measuring coils 7, 8 are arranged inside opposite air-gaps of the magnetic circuit and are connected in an electric measuring circuit in series with each other and in parallel to voltage dividers 12, 13 and 14, 15. The alternating current components induce voltages in the coils 7 and 8 which add up, the sum thereof appearing across the series-connection of resistors 13, 15. This voltage is integrated by an integrating circuit 10 and then filtered in a band-pass filter 11. The magnetic circuit 5, 6 is screened by lateral screening members 30, 31 so that the remaining field lines of a lateral parasitic magnetic field produce in the magnetic circuit flux portions which are approximately equal and which are added to the useful flux in one air-gap and are substracted from the useful flux in the other air-gap.

Abstract: A self-excited microelectromechanical device is described. The device includes a resonating structure, such as a cantilever, which responds to a physical phenomenon by generating an induced variable frequency voltage signal corresponding to the physical phenomenon. Self-excitation circuitry connected to the cantilever processes the induced variable frequency voltage signal and produces a variable frequency voltage signal in a resonant pass band of interest that is applied to the cantilever to augment the effect of the physical phenomenon on the cantilever. An exemplary use of the device is as a power meter. In this context, the cantilever responds to the electric field associated with a power signal on a metered line. The cantilever transforms the voltage signal of the electric field into a corresponding frequency signal. The noise-immune frequency signal can be readily processed to reconstruct the power signals carried by the power line.

Abstract: A self-excited microelectromechanical device is described. The device includes a resonating structure, such as a cantilever, which responds to a physical phenomenon by generating an induced variable frequency voltage signal corresponding to the physical phenomenon. Self-excitation circuitry connected to the cantilever processes the induced variable frequency voltage signal and produces a variable frequency voltage signal in a resonant pass band of interest that is applied to the cantilever to augment the effect of the physical phenomenon on the cantilever. An exemplary use of the device is as a power line sensor. In this context, the cantilever responds to the electric field associated with a power signal on a power line. The cantilever transforms the voltage signal of the electric field into a corresponding frequency signal. The noise-immune frequency signal can be readily transmitted and processed to reconstruct the power signals carried by the power line.

Abstract: A current sensor has one signal interface channel including a transformer having a primary winding, a secondary winding and a feedback winding. A magnetic core magnetically couples the primary winding, the secondary winding and the feedback winding. The current sensor further includes a feedback generating circuit responsive to an AC signal in the secondary winding for generating a feedback signal having a continuous polarity supplied to the feedback winding. The feedback signal being effective for maintaining a flux in the magnetic core substantially near zero. The feedback generating circuit is made up of an operational amplifier, such as an amplifier having first and second differential input ports and first and second differential output ports, and a switching assembly designed to generate a compensating AC signal from a DC offset voltage. The compensating AC signal is conveniently coupled to the operational amplifier through the magnetic core.

Abstract: The internal and/or external magnetic fields of a coil are nullified to ad structurally detrimental Lorentz Forces and/or environmentally hazardous magnetic fields, in accordance with preestablished design objectives.

Abstract: A current sensor operating according to the compensation thereon which is particularly suited for acquiring high currents has a secondary winding of the current transformer is divided into at least two sub-windings that are supplied by different amplifiers in an amplifier arrangement. This results in symmetrical loading of the supply voltage so that twice as high a compensation current is enabled given the same internal resistance of the sub-windings and same resistance of the terminating resistor as in known current sensors of this type.

Abstract: The object of the present invention is to provide a small precise insulating type current sensor system.Sensing portion is composed of a magnetoresistance element, a bias conductor, and a current conductor, all of which are arranged on an insulating substrate. Resistance change of the magnetoresistance element is taken into an amplifier, and an output of the amplifier flows as a bias current to the bias conductor. When a current flows in the current conductor, the current causes a magnetic field and the resistance of the magnetoresistance element must be changed. However a feedback of the resistance change by the amplifier changes the bias current and controls the bias current for keeping the magnetic field of the magnetoresistance element at a constant. Accordingly, the insulation type current sensing with a wide range and preferable preciseness without being affected with a hysteresis of the magnetoresistance element and Barkhausen noise became possible.

Abstract: An improved method and apparatus for detecting signals on a twisted pair of transmission lines includes a sensor for nonintrusively coupling a portion of the signal to the apparatus. A filter is coupled to the sensor and filters unwanted frequencies from the signal. The signal is then amplified and optionally passed to an identification circuit which identifies the presence of high and low frequency signals. The signal is rectified creating a DC signal proportional to the detected signal's strength. An audio tone proportional to signal strength is generated and the tone is amplified and output.

Abstract: Current in a line is measured by passing it through a coil, having at least one turn, linking a small high permeability core; passing a measuring current through a bucking winding around the same core; and controlling the measuring current to buck the magnetomotive force of the line current so that the core flux stays below the saturation level. The measuring current may flow through a precision resistor so that a voltage across the resistor is an accurate measure of the line current. The measuring current is obtained from a high frequency switching circuit which senses the change of flux in the core. In normal operation the circuit switches when the core flux has risen to a predetermined value, such as 60% or 80% of the saturation value. If drift or extreme transients cause the flux to reach the saturation level, a sensing and correction circuit re-establishes operation between the desired points.

Abstract: A method and apparatus for detecting power lines including a pickup coil for detecting the magnetic field generated by the current conducted by a power line and for producing a sense current in response to the detected magnetic field, a gyrator circuit for generating a sense voltage in response to the sense current and tuning means for producing an output voltage in response to the sense voltage such that a power line can be detected thereby. The tuning means also tunes the power line detecting apparatus to the predetermined frequency of the current conducted by the power lines. The power line detecting method and apparatus also preferably analyzes the magnitude and frequency of the output voltage produced by the tuning means so as to distinguish output voltages generated in response to the magnetic fields produced by power lines from those generated by extraneous electromagnetic noise.

Abstract: An optical sensor comprising: a light irradiation means for irradiating a linearly polarized light having a wavelength of 740 to 890 nm; a magneto-optical element having a composition of Y.sub.3-X Tb.sub.X Fe.sub.5 O.sub.12 (0.3.ltoreq..times..ltoreq.0.8) for Faraday rotating the linearly polarized light to output a rotated polarized light; and a detecting means for modulating in intensity the rotated polarized light which has been Faraday rotated by the magneto-optical element and detecting a light output of the rotated polarized light from the magneto-optical element. This magneto-optical sensor has a high sensibility and an excellent temperature characteristics under condition of low-magnetic field. When the optical sensor 10 is additionally provided with an electro-optical element having Pockels effect in parallel to the magneto-optical element, it becomes possible to measure not only current intensity but also voltage intensity.

Abstract: An alternating current sensor includes a conductive pipe and a cylindrical-shaped conductive element preferably partially surrounded by the pipe. The pipe is substantially concentric to the conductive element and a conductor electrically connects a pair of corresponding ends of the pipe and conductive element to form a connected conductive path through the sensor. The pipe and the conductive element are spaced apart a predetermined radial distance to form a magnetic field in the space between the pipe and the conductive element during current flow along the connected conductive path. A flux sensor, such as an air-core coil, senses changes in magnetic flux over a sense region situated in the space between the pipe and the conductive element. A transformer having a saturable magnetic core is responsive to a magnetic field over a transformer region for generating a predetermined level of electrical current which can be used for safely powering various electrical circuits associated with the current sensor.

Abstract: A DC current sensor has a detecting core with a plurality of detecting core members adapted to be divided in a circumferential direction for receiving the lead wire. A pair of annular exciting cores on one of said detecting core members formed of saturable magnetic material has a core intersection inter-connected perpendicularly to the circumferential direction of said detecting core members, and are disposed oppositely in spaced relation with said detecting core members to magnetically saturate a portion thereof by a magnetic flux produced substantially in the perpendicular direction against a magnetic flux in the circumferential direction, produced by the DC current flowing through said lead wire being detected, and to interrupt a magnetic path by the magnetic flux in the circumferential direction periodically. Exciting coils are wound around the exciting cores in negative-phase excitation.

Abstract: A DC current sensor, comprising a detecting core consisting of an annular soft magnetic material having a hollow portion extending in a circumferential direction within the core; an excitation coil wound and disposed in a circumferential direction in the hollow portion; a detecting coil toroidally wound around the detecting core; a lead wire through which a DC current for non-contact detection flows, and extended through the center of the detecting core; an AC current supply for applying current to the excitation coil for periodically magnetically saturating the entire detecting core in both the circumferential and a direction perpendicular thereto, whereby the magnetic flux produced in the detecting core can be modulated according to the DC current flowing through the lead wire and being detected upon excitation of the excitation coil; and the detecting coil producing an electromotive force having a frequency twice the excitation current for detecting the DC current flowing through the lead wire.

Abstract: An optical sensor comprising: a light irradiation means for irradiating a linearly polarized light having a wavelength of 740 to 890 nm; a magneto-optical element having a composition of Y.sub.3-x Tb.sub.x Fe.sub.5 O.sub.12 (0.3.ltoreq.x.ltoreq.0.8) for Faraday rotating the linearly polarized light to output a rotated polarized light; and a detecting means for modulating in intensity the rotated polarized light which has been Faraday rotated by the magneto-optical element and detecting a light output of the rotated polarized light from the magneto-optical element. This magneto-optical sensor has a high sensibility and an excellent temperature characteristics under condition of low-magnetic field. When the optical sensor 10 is additionally provided with an electro-optical element having Pockels effect in parallel to the magneto-optical element, it becomes possible to measure not only current intensity but also voltage intensity.

Abstract: Direct current can be measured by passing a conductor carrying the current through the core of a toroidal transformer having a bias winding and a sensing winding. A pulse generator send pulses of magnetization current through the sensing winding so that the magnetization current produces a magnetic flux in the core which opposes a magnetic flux produced by the direct current carried by the conductor. A sensing circuit, connected to the sensing winding, detects the level of current through that winding to produce a measurement of the direct current carried by the conductor. A constant direct current is applied through the bias winding to increase the magnetic flux produced by the direct current carried by the conductor. Biasing the magnetic flux enables even small currents flowing through the conductor to be measured. Another version of the current sensor uses two transformers to measure direct current flowing in either direction in the conductor and provides an indication of that current's polarity.

Abstract: In combination, a gas turbine engine ignition system exciter, an igniter, a conductor that connects the exciter to the igniter to form a discharge circuit, and a current pulse detector for detecting current pulses in the circuit, the detector comprising a wire disposed in close proximity to a current carrying element in the circuit so that a sense current is induced in the wire across a coreless gap; the detector further comprising a signal conditioning circuit for converting the sense current to an output that indicates occurrence of a spark discharge.

Abstract: An electric current is measured by a device that includes a magneto-optical element which acts as a Faraday rotator wherein a plane of polarization of polarized light passing therethrough is rotated as a function of a magnetic field surrounding that element. A light emitter and polarizer send a polarized light beam through the magneto-optical element. First and second light detectors are located within the single beam of light emerging from the magneto-optical element. Associated with the two detectors are separate polarizers respectively oriented at -45 degrees and +45 degrees to a polarization plane of the light beam emerging from the magneto-optical element when no electric current flows through the conductor. The magnitude of the current in the conductor is determined by comparing signals from the two light detectors.

Abstract: The sensor head (1) is intended for a fiberoptic current measuring device. It exhibits a twisted low-birefringence LB fiber (14) which is guided around a current conductor (2) and serves to conduct polarized light. Using the LB fiber (14), the Faraday rotation of the polarized light, which rotation is generated by the magnetic field (H) of the current (J) to be measured, is detected. The LB fiber (14) is spliced at its two ends in each instance with one of two polarization-conserving, light-conducting HB fibers (6, 7), one (6) of which supplies the polarized light. The two HB fibers (6, 7) are secured in each instance in the vicinity of the two splice locations (19, 20) with the absorption of the torsional force generated by the twisting of the LB fiber (14).In spite of having a simple and sturdy structure, the sensor head (1) is distinguished by a high degree of measurement accuracy.

Abstract: An optical current transformer for measuring a current flowing through a conductor by transmitting a light beam about the current-carrying conductor includes four Faraday effect glass rods. For transmitting the light beam, the rods are arranged in a rectangle forming a through hole for the conductor. Three optical path changing pieces are included, each for redirecting the light beam from one of the glass rods to a different one of the glass rods, and each being positioned at a different corner of the glass rod rectangle. Two substrate plates, each having a through hole for the conductor, are positioned at opposite sides of the glass rod rectangle to sandwich the glass rods and the optical path changing pieces therebetween. The glass rods are substantially fixed while allowing for thermal expansion and contraction of the glass rods.

Abstract: A DC current sensor with an exciting core of soft magnetic material and formed with a pair of tubular bodies, each tubular body being positioned in parallel with the other to provide therebetween a space, through which passes a wire conducting a current to be detected; a detecting core formed with the side faces of a pair of tubular bodies and two plate-like members of soft magnetic material, each of which connecting integrally with each of the inside edges thereof near an opening of the tubular bodies to form a rectangular frame-shaped member as a whole; exciting coils, each of which magnetically energizing the exciting core in the direction perpendicular to the plane of the detecting core; detecting coils, each of which being wound around the detecting core; and applying an alternating current to the exciting coils to periodically and magnetically saturate the rectangular-shaped portions of the detecting core and exciting core, energizing the exciting coils to modulate a magnetic flux produced in the detect

Abstract: A magneto-optical element is of a rare-earth iron garnet crystal expressed at least by formula 1, and a element in whose composition range the value of X is set at 0.8.ltoreq.X.ltoreq.1.3; that of Y at 0.2.ltoreq.Y.ltoreq.0.4; that of Z at 0.1.ltoreq.Z.ltoreq.0.9; and that of W at 0.ltoreq.W.ltoreq.0.3; and R element is made at least one or more kinds of rare-earth elements. An optical magnetic field sensor is composed in such a manner that light diffracted by magnetic domain structure of rare-earth iron garnet crystal can be detected up to a higher-order light by optical fiber on light output side through optical system arrangement. A magnetic field measuring equipment composed of the optical magnetic field sensor has a linearity error of .+-.1.0% or less within a magnetic field range 5.0 Oe to 200 Oe, and allows a measuring accuracy higher than with prior art equipment.(Bi.sub.x Gd.sub.y R.sub.z Y.sub.3-x-y-z)(Fe.sub.5-w Ga.sub.w)O.sub.

Abstract: The present invention involves measurement of an electrical current by means of a current transformer having the current to be measured passing in an axial direction through the current transformer, and the voltage induced thereby in the windings of the current transformer are used to produce a first voltage. A Hall effect is used in series with the current transformer to produce a second voltage measurement corresponding to the current measured by the Hall effect sensor. When the two measurements agree to within a predetermined value (typically 5% of the root-mean-square current values measured by each sensor) then the current transformer reading is used as the more accurate. Otherwise, the Hall effect current sensor is used as the more accurate current measurement.

Abstract: A voltage sensor is composed by arranging along the optic axis, successively from the side of incident light, a first polarizer, a Pockels cell for detection, a Pockels cell for modulation, and a second polarizer wherein an electric field proportional to a voltage to be measured is applied to the Pockels cell for detection, and a periodic electric field for modulation that varies the phase difference by 2n.pi. radians, where n is a positive integer, during each period and that has a frequency higher than the electric field applied to the Pockels cell for detection is applied to the Pockels cell for modulation, and the voltage to be measured is determined based on a phase change in the intensity of the light output from the second polarizer.

Abstract: A DC current sensor using a continuous annularly-shaped detecting core of soft magnetic material; a continuous annularly-shaped exciting core of soft magnetic material intersecting with the detecting core perpendicular to the plane thereof; respective detecting and exciting coils wound respectively around the detecting and the exciting cores; an AC excitation of a given frequency applied to the exciting coil to saturate the detecting core; a wire conducting DC current to be detected extending through the detecting core to establish a magnetic flux therein; and a detector connected to the detecting coil for detecting the magnetic flux modulated by the AC excitation to detect the DC current flowing in the wire.

Abstract: A first Hall element is supplied with a current proportional to a load voltage and applied with a magnetic field proportional to a load current and produces a voltage proportional to a load power given by the load voltage and the load current. A second Hall element has the same characteristic as that of the first Hall element and supplied with the current proportional to the load voltage and no magnetic field. The output voltages of the first and the second Hall elements are combined by combining means to compensate and remove an offset voltage component contained in the output voltage of the first Hall element.

Abstract: Measurements, particularly of current, using the Faraday magneto-optic effect in an optical fibre, have suffered from inaccuracy due to vibration causing linear birefringence in the fibre. Current measurement according to the method and apparatus employs an optical fibre (3) coiled round a conductor (6) carrying the current to be measured. A laser (1) launches two counter propagating light beams into the fibre by way of a beam splitter (2) and directional couplers (4,5). Polarization beam splitters (7,8) derive two pairs of orthogonally linearly polarized light beams, one from each direction of propagation. These beams are passed to detectors (10,11,12,13) having outputs coupled to a processor (14). An output signal is derived by the processor which is representative of the non-reciprocal Faraday rotation but independent of reciprocal birefringent effects, including linear birefringence due to vibration. Thus the output signal is representative of current in the conductor.

Abstract: A current sensor for measuring a primary electrical current inducing a primary magnetic field defined over a known region includes a first sensor unit for measuring the line integral of the primary magnetic field along a first predetermined path included within the known region; and a second sensor unit for measuring the line integral of the primary magnetic field along a second predetermined path within the known region, the line integral of the primary magnetic field measured by the second sensor unit being a predetermined calibrated amount different from the line integral of the primary magnetic field measured by the first sensor unit. The current sensor further includes a current source for generating a current inducing a magnetic field to partially offset the difference between the line integral of the primary magnetic field measured by the first sensor unit and the line integral of the primary magnetic field measured by the second sensor unit.

Abstract: An electro-optics current sensing system for sensing and avoiding thermally induced measurement errors in a current sensor includes a beam generator, such as a light emitting diode or a laser diode, thermally coupled to the current sensor for encoding into the optical beam supplied by the beam generator both temperature and sensed current information. An electro-optics (E/O) demodulator which includes a wavelength division multiplexer (WDM) demodulates the encoded optical beam to recover the temperature and sensed current information from a pair of demodulated signals which can be further processed for filtering resistivity changes from the sensed current measurement.

Abstract: The present inventors have discovered that a compact, highly sensitive current sensor can be made for any inductive component having an air gap in its magnetic path by disposing a layer of magnetoresistive material in the path of the fringing magnetic field. In the preferred embodiment, a thin magnetoresistive film of La.sub.w Ca.sub.x Mn.sub.y O.sub.z on a LaAlO.sub.3 /Al.sub.2 O.sub.3 substrate provides a high sensitivity in the range of 1-100 mV/ampere of DC current in the inductive component. The current sensor consumes a very small amount of power and provides the desirable electrical isolation between the sensor and the active device circuit.

Abstract: An alternating current sensor for measuring a primary alternating current inducing a magnetic flux density defined over a known region comprises: a first sensor for measuring changes in magnetic flux due to the primary current over a first predetermined area included within the known region; a second sensor for measuring changes in magnetic flux due to the primary current over a second predetermined area within the known region, the changes in magnetic flux measured by the second sensor being a predetermined amount different from the changes in magnetic flux measured by the first sensor; and a current source for generating a current inducing changes in magnetic flux over a third predetermined area to offset the difference between the changes in magnetic flux measured by the first sensor and the changes in magnetic flux measured by the second sensor.

Abstract: A current sensor includes first and second branches interconnected by a center conductor magnetically coupled to an annular current comparator for producing an output signal related, in magnitude and phase, to an input current. The input current divides, according to a predetermined relationship, between the first and second branches such that the current in the center conductor interconnecting the first and second branches is also related to the input current. A current is induced in the annular current comparator in relation to the current in the center conductor and, thus, in relation to the input current. Secondary windings are wound about and magnetically coupled to the annular current comparator for producing an output signal responsive to the current induced within the annular current comparator.

Abstract: An optical sensor includes: a light irradiation source for irradiating linearly polarized light having a wavelength of 740 to 890 nm; a magneto-optical element having a composition of Y.sub.3-x Tb.sub.x Fe.sub.5 O.sub.12 (0.3.ltoreq..times..ltoreq.0.8) for Faraday rotating the linearly polarized light to output a rotated polarized light; and a detector for modulating in intensity the rotated polarized light which has been Faraday rotated by the magneto-optical element and detecting a light output of the rotated polarized light from the magneto-optical element. This magneto-optical sensor has a high sensibility and excellent temperature characteristics under a condition of low-magnetic field. When the optical sensor 10 is additionally provided with an electro-optical element having a Pockels effect in parallel to the magneto-optical element, it becomes possible to measure not only current intensity but also voltage intensity.

Abstract: Apparatus for sensing or measuring a magnetic field comprises a light source (10) for generating light having at least a component which is polarized, a sensing element (16) arranged to transmit light from the source and comprising material having a substantial Verdet constant which depends on the temperature of the material, means (14-19, 21) for combining light from the source with light from the sensing element to form an interference pattern, means (23) for providing a signal representative of the intensity of the light so combined, and means for deriving first and second signals dependent on the Verdet constant of the material and the temperature thereof, respectively, from the signal representative of light intensity, whereby the intensity of the magnetic field at the element, substantially independent of temperature, can be derived. The invention extends to a method of sensing or measuring magnetic field intensity, and to apparatus and a method for sensing or measuring electric current.

Abstract: A noninductive shunt current sensor includes a cylindrical-shaped conductive element and a concentric conductive pipe electrically connected at one end by a conductor, such as a washer. Except for the conductor, the pipe and conductive element are electrically isolated from each other by insulation, such as a polyimide or an air-gap. Sensing wires are electrically connected to contact points, each contact point being located on either the inner surface of the inner pipe or the outer surface of the outer pipe. The wires pass through a space where the magnetic field is substantially null, thereby minimizing any mutual coupling effects. A magnetic core and a coil can be situated between the pipe and the conductive element to provide an electrical self-power capability to the noninductive shunt current sensor.

Abstract: A Rogowski coil is used as a precise current and temperature measuring device (in particular a device that is highly insensitive to temperature variations). The Rogowski coil is of the type including at least one printed circuit plate provided with a circular cutout. The coil is implemented by metal deposits on each of the two faces of the plate and extending along radii such that geometrical projections thereof pass through the center of the cutout. Electrical connections between the radii on one face and those on the opposite face are implemented by plated-through holes that pass through the thickness of the plate.

Abstract: A power multiplication circuit including a Hall element for generating between voltage output terminals thereof a first output voltage corresponding to a power of a system under measurement. The circuit further includes a voltage polarity detection circuit for detecting a polarity of a power source voltage of the system and an operating circuit connected to receive the first output voltage and the polarity for amplifying the first output voltage and for changing over between amplified first output voltage and an inverted voltage of the amplified first output voltage to generate a second output voltage in accordance with the polarity. The circuit also includes an integrating amplifier circuit for integrating the second output voltage to generate an integrated signal and a variable resistance element connected between one of the voltage output terminals of the Hall element and ground, and connected to receive the integrated signal.

Abstract: A current sensor for measuring a primary electrical current inducing a magnetic flux density defined over a known region comprises: a first sensor for measuring magnetic flux due to the primary current over a first predetermined area included within the known region; and a second sensor for measuring magnetic flux due to the primary current over a second predetermined area within the known region, the magnetic flux due to the primary current measured by the second sensor being a substantially predetermined calibrated amount different from the magnetic flux due to the primary current measured by the first sensor. The current sensor may further include a current source for generating a current inducing a magnetic flux density within the known region to at least partially offset the difference between the magnetic flux due to the primary current measured by the first sensor and the magnetic flux due to the primary current measured by the second sensor.

Abstract: The present invention relates to an apparatus and a method for measuring the current in a high voltage overhead line (A). The apparatus comprises at least one device (2) for detecting and measuring the magnetic field induced by the line (A), the detector being arranged on the ground adjacent the line (A), the current being deduced by calculation.