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Sensors: Touch, Force, and Torque
Published in Richard L. Shell, Ernest L. Hall, Handbook of Industrial Automation, 2000
There are two approaches to the design of touch or tactile sensors based on magnetic transduction. Firstly, the movement of a small magnet by an applied force will cause the flux density at the point of measurement to change. The flux measurement can be made by either a Hall effect or a magnetoresistive device. Second, the core of the transformer or inductor can be manufactured from a magnetoelastic material that will deform under pressure and cause the magnetic coupling between transformer windings, or a coil’s inductance, to change. A magnetoresistive or magnetoelastic material is a material whose magnetic characteristics are modified when the material is subjected to changes in externally applied physical forces [9]. The magnetorestrictive or magnetoelastic sensor has a number of advantages that include high sensitivity and dynamic range, no measurable mechanical hysteresis, a linear response, and physical robustness.
Nanosensors for Societal Benefits
Published in Vinod Kumar Khanna, Nanosensors, 2021
Magnetoelastic sensors, made from amorphous ferromagnetic alloys of Fe, Ni, Mo, and B, vibrate mechanically under the influence of a time-varying magnetic field at a characteristic resonance frequency, producing a magnetic flux, which is remotely detected by a pick-up coil to provide wireless sensing. For sensor fabrication, 20-mm long magnetoelastic sensors are cut from the alloy: Fe40Ni38Mo4 B18 (Lin et al. 2010). The uncoated sensor has a resonance frequency of 102.5 kHz in air. It is ultrasonically cleaned and coated with polyurethane.
Magnetic Sensors
Published in John Vetelino, Aravind Reghu, Introduction to Sensors, 2017
Another magnetic sensor can be realized from magnetostriction or the magnetoelastic effect. The application of a magnetic field to a cylindrical rod will cause a stress, and this stress may change the length of the rod. If this happens, the inducted stress or changes in rod length become a measure of the applied magnetic field. In order to understand magnetostriction, consider the application of a magnetic field to a demagnetized ferromagnetic material, as shown in Figure 6.7.
Clinical potential of implantable wireless sensors for orthopedic treatments
Published in Expert Review of Medical Devices, 2018
Salil Sidharthan Karipott, Bradley D. Nelson, Robert E. Guldberg, Keat Ghee Ong
Another class of battery-free implantable sensors transmits measurements externally through interactions with magnetic fields [52], electromagnetic fields [53], or acoustic energies [54] provided by an external device. Typically, these sensors do not contain active electronic circuitry, but may still be composed of passive electronic components such as resistors, inductors, and/or capacitors. A common design of these sensors is the resonating circuit sensor [55]. The resonant frequencies of these sensors, which are dependent on the values of their inductor, capacitor, and resistor, vary with the parameter of interest. These sensors have been used in orthopedic implants [56] to measure tendon strain and elasticity. Compared to battery-powered sensors, these sensors have longer lifetime and are more robust because they do not contain internal batteries, complicated electronics, and telemetry systems [57]. Another type of passive implantable sensor is based on magnetoelastic materials [58] that can remotely convey physical information such as stress and pressure when interrogated via magnetic fields. Magnetoelastic materials are a class of magnetic materials that can efficiently convert magnetic energy to mechanical energy and vice versa. Typically, the magnetoelastic material is deposited or attached to the substrate, and then magnetized with a low-frequency magnetic AC field [59]. The magnetized sensor generates a magnetic field that is dependent on the applied mechanical loads. These sensors have been investigated in a preclinical model to monitor force loading at bone fixation plates [59], but have not yet been translated to clinical applications.
Pretensioned prestress friction losses considering contact imperfection at deviators in prestressed concrete girders
Published in Structure and Infrastructure Engineering, 2021
Meng Yan, Yongqing Yang, Xiaobin Li, Yi Bao, Jingfei Sun, Baolin Sun
Regarding measurement, magnetic flux sensors (force measurement accuracy: 1 N) were used to measure tensile forces in the tendons through the Villari effect (or magnetoelastic effect). At the time of tensioning the tendons, the magnetic properties of the tendons were changed (Budelmann, Holst, & Wichmann, 2014; Joh, Lee, & Kwahk, 2013; Wichmann, Holst, & Budelmann, 2009), so the actual tension force in the tendon could be evaluated. The cross-core sensor is installed by passing the tendon through the sensor for non-destructive testing, as shown in Figure 7. The magnetic flux sensors were pre-calibrated before the experiment.