The detection technology on wear debris in lubricating oil is critical to ensure the safe operation of the engines in the aerospace industry. In this article, a triple-coil reverse double-excitation solenoid sensor is discussed. Inside the sensor, electromagnetic field generated by two excitation coils is sensitive to the occurrence of wear debris, and its changes can be captured by the induction coil. Thus, the impedance and inductive voltage of the induction coil can be used to detect the wear debris. Assuming the debris is spherical, an electromagnetic model is established. Via time-harmonic electromagnetic field analysis method, the expressions of the induction coil’s impedance increment and inductive voltage are derived. The relationships between the impedance increment and the parameters of the debris and the coils are investigated. The theoretical results are validated by Maxwell from Ansys, Canonsburg, PA, USA, simulations and experiments. In order to get an accurate voltage output signal, a passband filter amplifier is designed to connect to the output of the induction coil and empirical mode decomposition is presented to process the digital voltage signal. The derivation method on the coil impedance increment and inductive voltage and the signal processing method can be extended to design sensors measuring more complicated wear debris.

Electromagnetic Sensor for Detecting Wear Debris in Lubricating Oil

Some of the strongest electromagnetic fields (EMF) are found in the workplace. A European Directive sets limits to workers’ exposure to EMF. This review summarizes its origin and contents and com pares magnetic field exposure levels in high-risk workplaces with the limits set in the revised Directive. Pubmed, Scopus, grey literature databases, and websites of organizations involved in occupational exposure measurements were searched. The focus was on EMF with frequencies up to 10 MHz, which can cause stimulation of the nervous system. Selected studies had to provide individual maximum exposure levels at the workplace, either in terms of the external magnetic field strength or flux density or as induced electric field strength or current density. Indicative action levels and the corresponding exposure limit values for magnetic fields in the revised European Directive will be higher than those in the previous version. Nevertheless, magnetic flux densities in excess of the action levels for periph eral nerve stimulation are reported for workers involved in welding, induction heating, transcranial magnetic stimulation, and magnetic resonance imaging (MRI). The corresponding health effects expo sure limit values for the electric fields in the worker’s body can be exceeded for welding and MRI, but calculations for induction heating and transcranial magnetic stimulation are lacking. Since the revised European Directive conditionally exempts MRI-related activities from the exposure limits, measures to reduce exposure may be necessary for welding, induction heating, and transcranial nerve stimulation. Since such measures can be complicated, there is a clear need for exposure databases for different work place scenarios with significant EMF exposure and guidance on good practices.

/pdf/the-revised-electromagnetic-fields-directive-and-worker-283bjvm9j5.pdf

The Revised Electromagnetic Fields Directive and Worker Exposure in Environments With High Magnetic Flux Densities

This paper presents the design, modeling, and calibration of an overactuated and actively controlled hexapole electromagnetic actuating system, which is implemented to stabilize and propel a microscopic magnetic particle in aqueous solutions. Compared to the 2-D quadruple magnetic tweezers in the paper by Zhang et al. ( IEEE/ASME Trans. Mechatronics , 2010) and the 3-D magnetic actuator in the paper by Zhang and Menq ( IEEE/ASME Trans. Mechatronics , 2011), the new electromagnetic actuating system achieves significantly greater force generation capability and much improved controllability of 3-D force in the workspace. These improvements are accomplished through enhanced design and synthesis of the six electromagnetic poles and improved current allocation of the overactuated system. A lumped parameter hexapole force model of the system is derived and validated through experimental calibration. It is then used to devise inverse modeling, which is implemented to realize real-time current allocation to enable the most effective manipulation of the 3-D magnetic force exerting on the particle at the center of the workspace. The system is designed for use with live cell experiments.

Actively Controlled Hexapole Electromagnetic Actuating System Enabling 3-D Force Manipulation in Aqueous Solutions

A prototype data acquisition and processing system for Schumann resonance measurements

The design and implementation methodology of a system to generate low-magnitude and low-frequency uniform magnetic fields on a specific volume using a tri-axial square Helmholtz coil is presented. The designing procedure is based on theoretical concepts and simulations from simple mathematical expressions that relate the area, with uniform magnetic field, with the length of the coils. Also, the computational model is constructed and simulated using finite element software. It is observed that theoretical results are consistent with simulation model results and the magnetic field measurement tests. It is concluded that the design methodology allows establishing a simplified and repeatable procedure to obtain a uniform magnetic field in the volume of interest suitable for in-vitro or in-vivo studies.

/pdf/metodologia-de-diseno-e-implementacion-de-un-sistema-para-38rdwr6uaq.pdf

Metodología de diseño e implementación de un sistema para generación de campos magnéticos uniformes con bobinas helmholtz cuadrada tri-axial

Naturally occurring electromagnetic oscillating fields in the very-low-frequency (VLF) range of the spectrum, i.e., from 1 to 200 kHz, are weak and difficult to detect under normal conditions. These naturally occurring VLF electromagnetic events are observed during thunderstorms, in certain mountain winds, and during earthquakes. On the other hand, man-made VLF electromagnetic fields are stronger and have been suspected of causing negative health effects. Typical sources of these VLF emissions include television sets, video display terminals (VDTs), certain medical devices, some radio stations, and the ground-wave emergency network (GWEN) used for military communications. This paper describes the development of a triaxial ldquoVLF gaussmeter,rdquo which can be made portable. This electronic system can be used to monitor VLF electromagnetic radiation in residential and occupational environments. The ldquoVLF gaussmeterrdquo is based on a microcontroller with a built-in 10-bit A/D converter and has been designed to measure the magnetic flux density and frequency across the wide VLF bandwidth (BW). A digitized resolution of 0.2 mG is used for the 0-200-mG range, and 2-mG resolution is used for the range of 2-2000 mG. The meter has been designed to include the following features: 1) automatic or manual range selection; 2) data logging; 3) single-axis mode; 4) peak hold; 5) RS-232 communication port; and 6) analog recorder output.

/pdf/very-low-frequency-electromagnetic-field-detector-with-data-1jx48dnh3f.pdf

Very-Low-Frequency Electromagnetic Field Detector With Data Acquisition

http://www.people.vcu.edu/~ymotai/Publications/conferences/MEASUR1561.pdf

Saba A. Hanna

Papers

Very-Low-Frequency Electromagnetic Field Detector With Data Acquisition

Measurement evaluations of static and low frequency magnetic fields in the near field region