Electrical current transducer (2) of a closed-loop type for measuring a primary current (I.sub.p) flowing in a primary conductor (1), comprising a fluxgate measuring head (7) and an electronic circuit (16) including a microprocessor (18) for digital signal processing. The measuring head includes a secondary coil (6) and a fluxgate detector (4) comprising an excitation coil and a magnetic material core. The electronic circuit comprises an excitation coil drive circuit (14) configured to generate an alternating excitation voltage to supply the excitation coil with an alternating excitation current (I.sub.fx), the secondary coil (6) connected in a feedback loop (12) of the electronic circuit to the excitation coil drive circuit (14), the electronic circuit further comprising a ripple compensation circuit (26, 28) configured to compensate for a ripple signal generated by the alternating excitation voltage.

Precision AC voltage, current, phase, power and energy measurements and calibrations with current ranges from 1 uA to 20 kA and voltage ranges from 1V to 1000 kV are now performed with accuracies of better than one part per million. Continued demand for improved accuracy has led the inventors to address improvements to dual stage and multi-stage current transducers that may form the basis of the measuring process within many of the measurement instruments providing the precision AC measurements and calibrations. Additionally, the improvements to dual stage and multi-stage current transducers provide for novel feedback controlled precision AC current sources without requiring measurement of the AC current source output directly.

A current transformer according to the present invention may comprise a magnetic core, a secondary coil, and a magnetic flux compensation member. A main circuit of an air circuit breaker penetrates the magnetic core. In addition, the secondary coil is arranged to be adjacent to the magnetic core, and a secondary current is induced through a current flowing in the main circuit. In addition, the secondary coil supplies the induced secondary current to a relay. The magnetic flux compensation member may be coupled to the magnetic core so as to correct magnetic flux of the secondary coil.

A sensor/transducer for use in reducing leakage current from a patient fluidly connected to a medical device by tubing filled with a conductive fluid (e.g., blood or dialysate (a “fluid line”)) includes a magnetically conductive core with 1) a centrally located support for a coil of fluid line, and 2) coiled electrical conductors located at positions that are spaced from the centrally located support, on opposite sides of the centrally located support. The sensor/transducer can be used to measure leakage current carried by the conductive fluid in the fluid line, or it can be used to induce current in the fluid line in a manner that reduces the leakage current.

A leakage current detection circuit and a fluxgate driver are provided. The leakage current detection circuit is suitable for a fluxgate device. The leakage current detection includes a duty cycle detection circuit, a compensation circuit, and a control signal generation circuit. The duty cycle detection circuit receives a pulse width modulation (PWM) signal from an inverter circuit. The duty cycle detection circuit detects a duty cycle of the PWM signal by sampling the PWM signal with a clock signal to output a count signal. The compensation circuit adjusts a pulse number of the count signal according to an offset signal in a self-test period. The control signal generation circuit calculates an average value of the count signal, and compares the average value with multiple threshold values to respectively generate multiple control signals. The control signals indicate a leakage current state of the fluxgate device.

A current sensing circuit is provided for measuring a current in an electrical line connecting an electrical supply to a load. The current sensing circuit includes a magnetic circuit having: a magnetic core, a reference winding wound around the magnetic core, and a conductor passing through center of the magnetic core. The conductor is being connected to the electrical line. The current sensing circuit further includes a detection circuit connected to the reference winding of the magnetic circuit. The detection circuit is configured to detect a change in condition of the magnetic core and generate a detection signal in response to determination of the change. Furthermore, the current sensing circuit includes a controller coupled to the detection circuit for receiving the detection signal. The controller measures the current in the electrical line in response to the detection signal from the detection circuit.

A current measuring device (1) includes two triaxial magnetic sensors (11, 12) that are arranged with a prescribed gap between the two triaxial magnetic sensors (11, 12) such that magnetic-sensing directions of the two triaxial magnetic sensors (11, 12) are parallel to each other, and a calculator configured to calculate a current (I) flowing in a measurement-object conductor (MC) based on detection results from the two triaxial magnetic sensors (11, 12) and a gap between the two triaxial magnetic sensors (11, 12).

Unique systems, methods, techniques and apparatuses of a power line measurement device are disclosed. One exemplary embodiment is a measurement device comprising a measurement device structured to at least partially surround a segment of a power distribution line, the measurement device including a winding portion spaced apart from the segment of the power distribution line structured to receive magnetic flux from the power distribution line and to output data corresponding to a current flowing through the power distribution line; and a magnetic shield spaced apart from the measurement device and positioned radially outward from the winding portion relative to the segment of the power distribution line, the magnetic shield comprising a first section and a second section coupled to the first section at an obtuse angle, the magnetic shield being structured to reduce an amount of external flux from being received with the measurement device.

In described examples, a magnetic sensor includes a waveguide that encapsulates dipolar molecules. A mm-wave electromagnetic field is launched into the waveguide, travels through the dipolar molecules, and is then received after passing through the dipolar molecules. The frequency of the mm-wave electromagnetic signal is swept across a range that includes an intrinsic quantum rotational state transition frequency (Fr) for the dipolar molecules. Absorption peaks in accordance with the Zeeman effect are determined. A strength of a magnetic field affecting the magnetic sensor is proportional to a difference in the frequencies of the absorption peaks.

A sensor device includes a current conductor designed to carry a measurement current, and a magnetic field sensor chip having a sensor element, wherein the magnetic field sensor chip is designed to detect a magnetic field at the location of the sensor element. The sensor device furthermore includes an encapsulation material, wherein the magnetic field sensor chip is encapsulated by the encapsulation material, and a soft magnet secured to the encapsulation material and designed to concentrate the magnetic field at the location of the sensor element. The magnetic field sensor chip and the soft magnet are galvanically isolated from one another by the encapsulation material.