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A microwave (MW) resonator to provide frequency-tunable and circularly polarized MW fields is proposed. This technology enlarges the range of application in optically detected magnetic resonance (ODMR) systems based on the diamond negatively charged nitrogen-vacancy (NV) center and enable the selective excitation of its electronic spins. The characteristics of this resonator are simulated and discussed via a series of experimental studies. An adjustable MW frequency (${f}_{MW}$) can be provided in the 2.5-3.1GHz range and the value of the input return loss (S11) corresponding to ${f}_{MW}$ measures <−15 dB which mean at least 96.84% coupling efficiency between the microwave resonator and the microwave source. When ${f}_{MW}$ is equal to the resonance frequency of the NV center (${f}_{NV}$) for different external magnetic fields (${B}$), the results of the ODMR experiment indicate that the fluorescence increases upon an increase in $\vert {B}\vert $. Finally, the resonator provides a circularly polarized MW output with a purity of 97.17%. This study paves the way to novel applications and to the development of magnetic sensing devices based on the NV ensemble in diamond. [ABSTRACT FROM AUTHOR]

This study proposes a magnetic sensor design and application for monitoring the health of rotor magnets in permanent magnet (PM) electrical machines through in-situ observation of the air-gap magnetic flux density. The reported device employs the concept of Fibre Bragg Grating (FBG) strain sensing fusion with magnetostrictive material to deliver a machine stator slot wedge integrated sensor that allows straightforward installation and retrofit with no invasive action to core elements of the machine. The sensing theory, design, prototyping, calibration and installation of the proposed magnetic sensing scheme are detailed in the paper. The sensor was installed into an inverter driven surface mount PM synchronous machine (SPMSM) and its performance for in-situ observation of rotor PM magnetization conditions validated in a range of healthy and demagnetised PM conditions tests. The obtained experimental data demonstrate the reported device’s capability to enable recognition of rotor PMs’ magnetisation level and thus their health monitoring. Finally, a fault index is proposed and experimentally validated that allows the application of in-situ magnetic sensor measurements for relative quantification of PM demagnetization fault severity. [ABSTRACT FROM AUTHOR]

This paper develops an electromagnet-based position measurement system for industrial actuators which offers significant advantages compared with traditional position measurement systems. These advantages include low cost, non-contacting operation, easy installation, and robustness to magnetic disturbances. In the first embodiment of the sensor, the electromagnet is located on the stationary actuator housing while the sensor is mounted on the actuator’s moving piston rod. This requires power to be supplied to the electronics on a moving object, and therefore a second embodiment that eliminates this disadvantage is developed. The second embodiment locates both the electromagnet and the powered sensor on the stationary housing. A mu-metal film of high magnetic permeability is located on the moving piston. Due to its high magnetic permeability, a significant fraction of the magnetic field measured by the sensor is coupled through the piston of the actuator. Hence, as the piston position changes, the magnetic field measured by the sensor changes. This leads to an excellent position measurement system with high sensitivity. The experimental results show that the second position sensor embodiment can provide 1% accuracy in position measurement, can reject the influence of disturbances from magnetic objects and can measure positions for stroke lengths up to 20 cm. Longer stroke lengths can be handled using additional daisy-chained sensors. [ABSTRACT FROM AUTHOR]

Magnetic sensing based on nitrogen-vacancy (NV) center ensembles provides unique signal-to-noise ratio and sensitivity for physical and biological measurements at room temperature. However, inhomogeneous microwave (MW) coupling with NV ensembles and different field projections onto the NV axes lead to nonsynchronous spin dephasing and pose severe challenges to magnetic sensing. In this paper, we experimentally investigated the impact of the MW field uniformity on the DC magnetic sensing based on NV ensembles. We obtained different MW field uniformity between 42% and 93% in the same direction using a square split ring resonator. The uniformity and direction of the MW field was mapped using a wide-field magnetic imaging system. The magnetic sensing with the MW frequency modulation technology confirmed the consistence between the theoretical analysis and experimental results. The sensitivity was enhanced by nearly seven times with the best MW field uniformity. Our study can promote the further application and development of magnetic sensing devices based on solid-state spin ensembles. [ABSTRACT FROM AUTHOR]

Three-phase three-core distribution power cables are widely deployed in power distribution networks and are continually being extended to address the ever-increasing power demand in modern metropolises. Unfortunately, there are high risks for the repair crew to operate on energized distribution power cables, which can cause deadly consequences such as electrocution and explosion. The predominant energization-status identification techniques used today are either destructive or only applicable to un-shielded power cables. Moreover, the background interferences affect the sensing technique reliability. In this paper, we have developed a non-destructive energization-status identification technique to identify energized three-phase three-core distribution power cables by measuring magnetic fields around the cable surface. The analysis shows that the magnetic-field-distribution pattern as a function of azimuth around the cable surface of the energized (current- or voltage-energized) three-phase three-core distribution power cable is distinguishable from the de-energized one. The non-idealities of phase currents and cable geometry were also discussed, and the proposed method still works under these circumstances. The sensing platform for implementing this technique was developed accordingly, consisting of magnetoresistive sensors, a triple-layered magnetic shielding, and a data acquisition system. The technique was demonstrated on a 22-kV three-phase three-core distribution power cable, and the energized status of the cable can be successfully identified. The proposed technique does not damage cable integrity by piercing the cable, or exposing the repair crew to hazardous high-voltage conductors. The platform is easy to operate and it can significantly improve the situational awareness for the repair crew, and enhance the stability of power distribution networks. [ABSTRACT FROM PUBLISHER]

Polymer sheets with foamed, multilayered, compounded, and perforated structures are in great demand for various applications, such as liquid-crystal displays, secondary cells, and electronic circuit devices. A system with magnetic and optical sensing is developed to accurately measure the thickness of polymer sheets during manufacturing. Use of a calibration gauge drastically improves precision of sheet-thickness measurement without the need for a standard sheet. The calibrated system is shown to maintain a sheet thickness of 460 mum with a precision of plusmn 0.7% during manufacturing of a polyethylene terephthalate sheet 1250 mm in width. The calibration method does not require any special technical skills of the operator, which produces consistent and reliable results [ABSTRACT FROM PUBLISHER]