Magnetic Sensor

Vehicle detectors provide essential information about parking occupancy and traffic flow. To cover large areas that lack a suitable electrical infrastructure, wired sensors networks are impractical because of their high deployment and maintenance costs. Wireless sensor networks (WSNs) with autonomous sensor nodes can be more economical. Vehicle detectors intended for a WSN should be small, sturdy, low power, cost-effective, and easy to install and maintain. Currently available vehicle detectors based on inductive loops, ultrasound, infrared, or magnetic sensors do not fulfill the requirements above, which has led to the search for alternative solutions. This paper presents a vehicle detector which includes a magnetic and an optical sensor and is intended as sensor node for use with a WSN. Magnetic sensors based on magnetoresistors are very sensitive and can detect the magnetic anomaly in the Earth's magnetic field that results from the presence of a car, but their continuous operation would drain more than 1.5 mA at 3 V, hence limiting the autonomy of a battery-supplied sensor node. Passive, low-power optical sensors can detect the shadow cast by car that covers them, but are prone to false detections. The use of optical triggering to wake-up a magnetic sensor, combined with power-efficient event-based software, yields a simple, compact, reliable, low-power sensor node for vehicle detection whose quiescent current drain is 5.5 μA. This approach of using a low-power sensor to trigger a second more specific sensor can be applied to other autonomous sensor nodes.

Precise contactless DC and AC magnetic sensors are required by car industry, chemical industry, for measurement of power and many other applications. The emphasis is given on current sensors based on magnetic materials, but other methods are also mentioned for ...

Anisotropic Magnetoresistors (AMRs) and recently also Giant Magnetoresistors (GMRs) are the latest competitors of small-size fluxgate sensors. AMR bridges using barber-pole geometry are linear devices; their performance can be improved by periodical flipping. GMRs may be ...

Now-a-days the security becomes a major issue in all the facets of human life. Security and safety are the most considered objectives in today’s world. To secure the property against theft, crime, fire, etc. a powerful security system is required not only to detect but also pre-empt hazards. This project is aimed at developing an advanced security alert system to detect and allow only the authorized persons into a high security zone like the vital defense establishments, nuclear installations and power plants, or in any smart environments. When a sensor is triggered by unwanted action, it first asks for One-time password (OTP) which will be sent to the authorized person’s mobile numbers as preferred by the owner of this instrument.

Fluxgate magnetometers with different design and core materials have been made. The sensors have been characterized and the frequency responses of the sensors have been measured. The fluxgate magnetometer based on orthogonal design and amorphous ...

In this paper a double axis planar micro-Fluxgate magnetic sensor is presented. The ferromagnetic core material, the Vitrovac 6025 X, has been deposited on top of the coils with the DC-magnetron sputtering technique, a new type of procedure with respect the existing solutions in the field of Fluxgate sensor. This procedure allows us to obtain a core with the good magnetic properties of the amorphous ferromagnetic material, typical of a core 25 mum thick, but with a thickness of only 1 mum, typical of a core electrodeposited. The micro-Fluxgate has been realized in a 0.5 mum CMOS process using copper metal lines to realize the excitation coil and aluminum metal lines for the sensing coils. Applying a triangular excitation current of 18 mA peak at 100 kHz the magnetic sensitivity achieved is about 0.45 mV/muT, suitable for detecting the Earth's magnetic field (plusmn50 muT), while the linearity error is 1.15% of the full scale. The maximum angle error of the sensor, evaluating the Earth magnetic field, is 3.4deg. The power consumption of the sensor is about 13.7 mW

SUMMARY Homing pigeons appear to use the earth's magnetic field as a compass and perhaps as part of their position-finding system or 'map'. The sensory system they use to detect magnetic fields is unknown, but two current possibilities are some mode of response by the pineal organ or by the visual system, or it may be based on the magnetite crystals found in their heads. Three series of experiments to test the involvement of magnetite are reported here. The alignment of the permanent magnetic domains in the birds heads was altered by (a) demagnetizing the birds, (b) magnetizing them with a strong magnetic field and (c) exposing the birds to a strong magnetic gradient. None of these treatments had a marked effect on the pigeon's orientation or homing under sunny skies, but a few results obtained under overcast skies suggest that demagnetizing the birds may have increased the scatter of their vanishing bearings. Perhaps pigeons use one magnetic sensor for their mag...

We present a novel approach to the detection of weak magnetic fields that takes advantage of recently developed techniques for the coherent control of solid-state electron spin quantum bits. Specifically, we investigate a magnetic sensor based on Nitrogen-Vacancy centers in room-temperature diamond. We discuss two important applications of this technique: a nanoscale magnetometer that could potentially detect precession of single nuclear spins and an optical magnetic field imager combining spatial resolution ranging from micrometers to millimeters with a sensitivity approaching few femtotesla/Hz$^{1/2}$.

Homing pigeons appear to use the earth's magnetic field as a compass and perhaps as part of their position-finding system or 'map'. The sensory system they use to detect magnetic fields is unknown, but two current possibilities are some mode of response by the pineal organ or by the visual system, or it may be based on the magnetite crystals found in their heads. Three series of experiments to test the involvement of magnetite are reported here. The alignment of the permanent magnetic domains in the birds heads was altered by (a) demagnetizing the birds, (b) magnetizing them with a strong magnetic field and (c) exposing the birds to a strong magnetic gradient. None of these treatments had a marked effect on the pigeon's orientation or homing under sunny skies, but a few results obtained under overcast skies suggest that demagnetizing the birds may have increased the scatter of their vanishing bearings. Perhaps pigeons use one magnetic sensor for their magnetic co...

Incorporating an analytical approach to simulate the interaction of a series of long cracks and the induced current of a double-D excitation coil, we have developed a model-based method to do precise detection of the positions of the cracks in a metallic structure by using eddy-current superconducting quantum interference device (SQUID) nondestructive evaluation (NDE) measurements. Conventionally, the structure of the defects is found by iteratively solving a numerical forward problem, which is usually based on finite-element, boundary-element, or volume-integral method. This, however, incurs a heavy numerical burden, as every time the forward problem is to be solved, a rigorous numerical model should be inevitably employed to extract the complex distribution pattern of the induced current encountering defects of the structure. In this paper, an analytical approach is used for the modeling of the interaction of the induced current and a series of cracks in the sample. It duly considers the distribution of the induced current in the flawed samples, does not call for extremely high computational resource, and thus permits efficient NDE as the forward problem can be solved within a reasonable time. Here, a high-Tc first-order radio-frequency SQUID gradiometer is employed as the magnetic sensor of the NDE system to scan the samples with different cracks. The accuracy of the proposed algorithm is verified by having the extracted shape of the defects obtained by applying the proposed algorithm on the SQUID NDE measurements against the actual cracks.

Magnetic tunnel junctions (MTJs), composed of two ferromagnetic electrodes separated by a thin insulating barrier layer, are currently used in spintronic devices, such as magnetic sensors and magnetic random access memories. Recently, driven by demonstrations of ferroelectricity at the nanoscale, thin-film ferroelectric barriers were proposed to extend the functionality of MTJs. Due to the sensitivity of conductance to the magnetization

We can note that in these days touch screen technology began to flourish and it is more widely used both in hardware and in different applications. A touch screen based interface is beginning to be a basic requirement in almost every mobile appliance, and at the same time demand to equip other products with this technology is on the rise.