Hall effect sensor

Abstract: The object of this book is to present the principles, instrument designs and applications of available magnetic transducers. In order to accomplish this task, the author begins with a fundamental chapter that focuses on the phenomenological magnetism, units and sensor specifications. The book continues by dedicating a full chapter to each magnetic sensor family: Induction, Fluxgate, Magnetoresistor, Hall effect, Magneto-optical, Resonance, SQUIDS and other principles. It ends with three chapters on applications, testing, calibration and magnetic sensors for non-magnetic variables. Various authors have contributed to some of the chapters. In spite of this, the content, presentation, opinion and notation are consistent throughout the book and uniform. Furthermore, each chapter can be read individually without losing its scope. The author(s) have focused on devices that are developed or under prototyping by commercial or public institutions. The book's objectives are also to get an insight into sensor design properties for a specific application and to understand the limitations and/or suitability of a specific sensor. Each chapter is therefore accompanied by an extensive list of scientific and technical material that provides a good reference for those interested in further reading. There are a number of books treating magnetic materials and their applications. However, often only a fundamental point of view is given. Magnetic Sensors and Magnetometers is a comprehensive book on the practice of magnetic transducers and their bases with many contributions from different experts in this field. Indeed, many professionals and researchers have (or will have) the need at some point for a magnetic sensor or transducer, and therefore a book of this nature is a very good reference for building and designing the most suitable solution for a specific application. It also provides design hints for connecting magnetic sensors to electronic devices, such as amplifier noise matching, etc. The book may also be of interest to teachers, students and researchers at universities, to instrumentation and application designers and users and the like. It is appropriate to list and comment on the various chapters for the reader to know what can be found in them: Basics (by Hauser and Ripka with 25 references): magnetic material types and properties and sensor specification. Induction Sensors (by Ripka with 29 refs) describes the air coils and their limitations, coils with ferromagnetic cores, amplifier noise matching, and other induction-based techniques such as rotating, moving, extracting and vibrating coils. Fluxgate Sensors (by Ripka with 159 refs) presents the principle of the transducer with different sensor geometries. Several aspects of this widely used type of sensor are discussed in more detail: demagnetization, core materials, second-harmonic analogue magnetometer, nonselective detection, short-circuited or current-output, noise and offset stability. Also, different design applications are described. Magnetoresistors (by Hauser and Tondra with 32 refs) illustrates the sensors and applications of the anisotropic magnetoresistance effect utilized in thin films and the giant magnetoresistance phenomenon. Hall-effect Magnetic Sensors (by Popovic et al with 51 refs) describes the basic sensor and thin-film Hall elements. Furthermore, integrated and multi-axes Hall sensors are presented. Magneto-optical Sensors (by Didosyan and Hauser with 33 refs) with the Faraday and Kerr effects and a description of the magneto-optical current transformer. Resonance Magnetometers (by Primdahl with 52 refs) describes the proton precession and the Overhauser variant effects and the optically pumped magnetometers. SQUIDs (by Fagaly with 38 refs) illustrates the sensors and operations with regard to noise and cancellation, input circuits, refrigeration and gradiometry. Other Principles (by Ripka and Kraus with 39 refs) describes, among others, magnetoimpedance, magnetoelastic and magnetostrictive sensors and biological applications. Application Magnetic Sensors (by Ripka and Acu na with 72 refs) in navigation, automotive, military, testing and planetary magnetic fields. Testing and Calibration Instruments (by Sasada et al with 38 refs) describes the application of magnetic coils and shieldings. Magnetic Sensors for Nonmagnetic Variables (by Ripka et al with 40 refs) is an interesting chapter on how to use magnetic properties to measure other physical effects like position, proximity, force, pressure, torque, current, etc. Appendix. Magnetic Sensors, Magnetometers and Calibration Equipment Manufacturers. It gives a fairly comprehensive list of manufacturers in the field. Overall, I recommend this book to professionals working in magnetism, magnetic instrumentation and related areas. It is highly relevant and contains an extensive and valuable amount of reference material. Jose M G Merayo

Abstract: A sensor for measuring linear displacement has a core of magnetic material disposed for movement within a bobbin about which a coil of insulated, electrically conductive wire is wound. At least one Hall effect device is disposed about the coil. The sensor is contained with a magnetic housing. When the coil is excited by a DC power source, the direction of magnetic flux flowing through the Hall effect device is dependent upon the position of the core.

Abstract: A Hall sensing apparatus having a large dynamic range is adapted for generating a current signal substantially in phase with the current in a conductor. The Hall sensing apparatus has a magnetic field concentrator assembly with oppositely disposed pick-up plates, each with a centrally attached concentrator rod for being symmetrically positioned on either side of the conductor. A Hall sensor element is wholly positioned in the space between the ends of the rods remote from the plates. A current circuit, having an externally controlled current varying device and temperature drift control device in series with a current source, provides a Hall current through the sensor element. A detection circuit, coupled across the width of the sensor element, provides an inverted and non-inverted signal in phase with the conductor current which are coupled to the inverting input of a summing amplifier. A reference voltage is then coupled to the non-inverting input of the summing amplifier to generate a dc bias offset control signal which is coupled, in a negative feedback configuration, to control the Hall current and thereby decrease the dc offset bias.

Abstract: The most important milestone in the field of magnetic sensors was when AMR sensors started to replace Hall sensors in many applications where the greater sensitivity of AMRs was an advantage. GMR and SDT sensors finally found applications. We also review the development of miniaturization of fluxgate sensors and refer briefly to SQUIDs, resonant sensors, GMIs, and magnetomechanical sensors.

Abstract: An apparatus includes an end effector, an energy component, a control module, and a directional force sensor assembly associated with the energy component and control module. The directional force assembly can include a piezoelectric disc, a piezoresistive element, an accelerometer, and/or a Hall Effect sensor. The end effector of the apparatus can include ultrasonic blade, an RF electrode. or a staple driving assembly. In some versions, the energy component includes an ultrasonic transducer. The control module may be configured to operate the energy component at a first energy setting in response to a first detected force and at a second energy setting in response to a second detected force. The apparatus may also include an activation feature to be operated by a user. In some versions the piezoelectric disc may include a plurality of segments and may be configured to induce movement in at least part of the energy component.