Direct Current Sensor Research Articles

A fiber Bragg grating direct current sensor with temperature compensation based on electromagnetic force

A novel fiber Bragg grating direct current sensor with intrinsic temperature compensation is presented in this article. The operating principle of the sensor is based on the deflection of a cantilever beam due to the electromagnetic force between a static-iron and a moving-iron attached to the free end of the cantilever which is enclosed within a solenoid through which the current under test is passed. The deflection of the cantilever beam is measured by differential strain sensing using two fiber Bragg gratings mounted on either side of the beam, thus achieving temperature compensation. The sensor operation is theoretically described, and experimental measurements confirm the operation of the fiber Bragg grating direct current sensor up to 500 A. A 382-pm Bragg wavelength shift difference is detected when the current is 500 A. The test results are analyzed and discussed in the time domain and frequency domain. The resistance to electromagnetic interference immunity of the fiber Bragg grating sensor is improved compared with the strain gauge sensor.

Magnetostrictive stress reconfigurable thin film resonators for near direct current magnetoelectric sensors

The magnetic response of microdevices is significantly enhanced at structural resonance allowing for improved sensitivity and signal-to-noise ratio. Here, free-standing thin film CoFe bridge resonators have been fabricated and investigated. It is shown that the strong magnetic field dependence of the fundamental resonance frequency is a function of magnetic field orientation due to stress-induced anisotropy. These devices may offer a new approach for developing fully integrated resonant magnetic field sensing technology.

Developing integrated piezoelectric direct current sensor with actuating and sensing elements

A cantilever-based, oscillating type MEMS direct current sensor (abbreviated as DC sensor), integrated with both actuating and sensing piezoelectric plates, as well as a micromagnet is proposed to satisfy the increasing needs of DC power supply for monitoring electrical consumption by either a single-wire or two-wire appliance cord. A prototype MEMS DC sensor, with a measured resonant frequency of 23 Hz, was microfabricated and characterised. In the case of a two-wire electrical appliance cord, it was found that the change in the peak-to-valley value (abbreviated as P-V value) of the output voltage was approximately proportional to the applied DC, and increased from 10.4 to 43.2 mV when the DC increased from 0 to 2 A under an excitation voltage of 5 Vpp. The shift of the resonant frequency because of the applied DC is believed to account for the change in the P-V value (or the maximum value) of the output voltage. In summary, the proposed MEMS DC sensor integrated with both actuating and sensing piezoelectric plates was observed to measure the output voltage constantly and linearly over the applied DC directly in a two-wire appliance without using a cord separator.

Integrated piezoelectric direct current sensor with actuating and sensing elements applicable to two-wire dc appliances

A cantilever-based oscillating type MEMS dc current sensor integrated with actuating and sensing piezoelectric plates and a micromagnet was proposed for measuring electricity consumption in a single-wire or two-wire appliance cord. A prototype MEMS dc current sensor, with a resonant frequency of 32 Hz, was microfabricated and characterized. In the case of a two-wire electrical appliance cord, it was found that the relative change in the maximum value of the output voltage is approximately proportional to the applied dc current. The output voltage increased from 0 to 10 mV when the dc current was increased from 0 to 2 A under an excitation voltage of 6 Vpp. At the same time, the resonant frequency shift of the cantilever was observed to be monotonically increased over the applied dc current both theoretically and experimentally. In summary, the proposed MEMS dc current sensor was demonstrated to measure the output voltage constantly and nearly linearly over the applied dc current in a two-wire appliance without using a cord separator.

DC humidity sensing properties of BaTiO 3 nanofiber sensors with different electrode materials

Barium titanate (BaTiO 3) nanofibers were synthesized by electrospinning and calcination techniques. Two direct current (DC) humidity sensors with different electrodes (Al and Ag) were fabricated by loading BaTiO 3 nanofibers as the sensing material. Compared with the Al electrode sensor, the Ag electrode sensor exhibits larger sensitivity and quicker response/recovery. The current of Al electrode sensor increases from 4.08 × 10 −9 to 1.68 × 10 −7 A when the sensor is switched from 11% to 95% relative humidity (RH), while the values are 2.19 × 10 −9 and 3.29 × 10 −7 A for the Ag electrode sensor, respectively. The corresponding response and recovery times are 30 and 9 s for Al electrode sensor, and 20 and 3 s for Ag electrode sensor, respectively. These results make BaTiO 3 nanofiber-based DC humidity sensors good candidates for practical application. Simultaneously, the comparison of sensors with different electrode materials may offer an effective route for designing and optimizing humidity sensors.

The field dependence of magnetoelastic damping in magnetostrictive material and its application in the magnetic field sensing

The magnetoelastic damping in magnetostrictive material is investigated. It is noted that the quality factor （the inverse measure of damping） of giant magnetostrictive material Terfenol-D is strongly dependent on bias direct current （DC） magnetic field. Taking advantage of the DC field dependence of magnetoelastic damping in magnetostrictive material, a DC or quasistatic magnetic sensor is proposed. The sensor is designed as a composite piezoelectric transformer （CPT） which is fabricated by bonding magnetostrictive material and piezoelectric transformer in layers. Theoretical analysis shows that the output voltage of the CPT is directly proportional to the quality factor of the CPT. Therefore, the output voltage of the CPT also strongly depends on DC field due to the strong field dependence effect of quality factor in magnetostrictive material. In addition, the ΔE effect of magnetostrictive material has little influence on the magnitude of the output voltage. A Terfenol-D/PZT8 composite transformer is fabricated for experiment. The experimental results show that the output sensitivity to DC field achieves ~5.12 mV·Oe-1 when the CPT is driven near resonance by an AC voltage with amplitude of 0.5 V.

Development of Direct Current Sensor using Magnetostriction

Development of Direct Current Sensor using Magnetostriction

Flaw detection using dc magnetic field measurement

Detection of internal flaws in conducting materials with considerable thickness is difficult using eddy current tests. This paper presents an alternative method, which uses dc magnetic field excited by the current impressed across the conducting material. In this case the internal flaws give rise perturbations of current flow and consequently the magnetic field is also changed. Perturbations in the magnetic field can be detected by dc (direct current) sensors such as magnetoresistive or Fluxset sensors. In this work numerically performed experiments are presented to recover flaws at the interfaces of metal parts jointed at high temperature by high intensity pressure.

Breakout box and circuits for direct injection experiments of electromagnetic susceptibility of aircraft electronics

Often the determination of the electromagnetic susceptibility of an aircraft's electronics includes direct injection experiments. In that case, an interfering signal, possibly CW and/or transient in nature, is applied directly to the data bus and signal lines of the aircraft system under test. In the past, the frequency or spectrum of the injected signal was typically in the VHF regime and lower (<150 MHz). Recently, susceptibility of aircraft components to signals with spectrums to 1 GHz and higher have been of interest. Application and measurement of signals in these frequency regimes must he made with greater care since cable and component physical and electrical lengths can become significant fractions of a wavelength at the highest frequencies of interest. This paper describes a breakout box designed for narrow and wideband high-voltage direct injection experiments of aircraft 1553 bus systems to 1 GHz and higher. A description is given of the breakout box. Also presented is the design and analysis of the direct injection circuit, the voltage and current sensors, and the high-voltage wideband divider board. Frequency domain characterizations of the circuits are presented, and an example of wideband transient pulse injection, measurement, and compensation using the breakout box is given.