Compact Current Sensor Research Articles

A Low-Cost Current Sensor Based on Semi-Cylindrical Magnetostrictive Composite

This paper presents the design, fabrication, and characterization of a compact current sensor based on magnetostrictive composites and resistance strain gauges. Firstly, we designed three kinds of current sensors with different structures, in which the shape of the giant magnetostrictive material (GMM) was cuboid, cylindrical, and semi-cylindrical. A set of finite element method (FEM) simulations were performed to qualitatively guide the design of three prototypes of the current sensor. It was determined that the most ideal shape of the GMM was semi-cylindrical. Secondly, Terfenol-D (TD) powder and epoxy resin were mixed to prepare magnetostrictive composites. In this paper, magnetostrictive composites with different particle size ranges and mass ratio were prepared and tested. The results show that the magnetostrictive composites had the best performance when the particle size range was 149–500 μm and the mass ratio of epoxy resin to TD powder was 1:5. Finally, this paper tested the performance of the sensor. The sensitivity, repeatability, and linear working range of the sensor reached 0.104 με/A, 2.51%, and 100–900 A respectively, when only 0.31 g of TD powder was employed. This means that current measurement with low cost, high sensitivity, and wide range was realized.

Compact microwave kinetic inductance nanowire galvanometer for cryogenic detectors at 4.2 K

We present a compact current sensor based on a superconducting microwave lumped-element resonator with a nanowire kinetic inductor, operating at 4.2 K. The sensor is suitable for multiplexed readout in GHz range for large-format arrays of cryogenic detectors. The device consists of a lumped-element resonant circuit, fabricated from a single 4 nm-thick superconducting layer of niobium nitride. Thus, the fabrication and operation is significantly simplified in comparison to state-of-the-art current readout approaches. Because the resonant circuit is inductively coupled to the feed line the current to be measured can directly be injected without having the need of an impedance matching circuit, reducing the system complexity. With the proof-of-concept device we measured a current noise floor δImin of 10 pA/Hz1/2 at 10 kHz. Furthermore, we demonstrate the ability of our sensor to amplify a pulsed response of a superconducting nanowire single-photon detector using a GHz-range carrier for effective frequency-division multiplexing.

A New Compact Fluxgate Current Sensor for AC and DC Application

This paper presents a compact current sensor for the measurement of ac and dc. The sensor consists of two toroidal magnetic cores. One core works in fluxgate principle to measure dc and low-frequency ac, and the other one is used as a current transformer for higher frequency application. The closed-loop configuration with a magnetic core and feedback winding in the sensor improved the sensitivity of the sensor, eliminated the offset and drift related to temperature, and greatly reduced the error caused by magnetic hysteresis phenomenon. It can measure currents up to 20 A, has an accuracy of 0.7% and ~30-kHz bandwidth.

Microfibre Mach–Zehnder interferometer and its application as a current sensor

The authors demonstrate a microfibre Mach-Zehnder interferometer (MMZI) using a single silica optical microfibre fabricated using flame-heated-drawing technique. The microfibre was cut into two parts: the first part is stretched straight, whereas the second part is bent and manipulated to form an MMZI. The fabricated MMZI shows good interference fringes with the highest extinction ratio of 14-dB. The free spectral range (FSR) of the interferometer can be tuned from 0.14 to 0.75-nm by micromanipulating the path-length difference of the MMZI under an optical microscope. It is also observed that the FSR is unaffected by the volatility of the surrounding air. The MMZI is also used to demonstrate a compact current sensor. The proposed sensor uses a copper wire, which touching one arm of the MMZI so that the wavelength shift is linearly proportional to the square of the amount of the flowing current. The slope efficiency of the sensor is obtained at 60.17-pm/A 2 .

Current sensor based on microfiber knot resonator

A compact current sensor using a microfiber knot resonator (MKR) is demonstrated. With the assistance of a copper wire that is wrapped by the microfiber knot, resonant wavelength inside the MKR can be tuned by applying electric current to the copper wire. The resonant wavelength change is based on the thermally induced optical phase shift in the MKR due to the heat produced by the flow of electric current over a short transit length. It is shown that the wavelength shift is linearly proportional to the square of the amount of current and the maximum tuning slope of 51.3 pm/A 2 is achieved using a newly fabricated MKR.

An interferometric current sensor based on optical fiber micro wires

In this paper we demonstrate a compact current sensor using the optic fiber micro wire, based on the idea of interferometrically measuring the thermally induced optical phase shifts as a result of heat produced due to the flow of electric current over short transit lengths. A responsivity of 1.28 x 10(-4) rad/I(2) at 50 Hz of current signal has been shown, with capability of measuring alternating current signals up to 500 Hz.

Effective Use of Miniature Multipoint Field-Based Current Sensors Without Magnetic Cores

A methodology for decoupling cross-coupled fields in compact current-sensor designs is presented. The compactness of the current sensor is made possible by using highly sensitive field detectors, such as giant magnetoresistive (GMR) technology, which offers galvanic isolation, small size (~ mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), and high bandwidth (> 1 MHz). By using known geometric relations between the conductor geometries and locations of the field detectors, cross-coupled magnetic-field signals can be used to extract necessary current signals, as well as separate unknown disturbance fields. This methodology can also be used to simplify the magnetic biasing required of GMR field detectors, including decoupling of the temperature dependence of the biasing magnet. Moreover, the methodology can also be extended to estimate the temperature of the magnet to provide an extra temperature signal for thermal management algorithms.