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Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The following performance criteria should be evaluated prior to an accelerometer’s use. The first three are most critical and for a given design are interrelated, representing the likely trade-offs or compromises in accelerometer selection. Sensitivity. Defined as the ratio of change in output to change in acceleration, sensitivity is expressed as coulomb/g or volt/g, depending on accelerometer type. The higher the sensitivity, the greater the system signal-to-noise ratio will be.Frequency response. Both low-and high-frequency response may be important to an application.Mass and size. Accelerometer weights can range from 1 to 60g. Typically, minimizing size and mass is desirable.Mass loading effect. Mounting an accelerometer with finite mass onto a structure changes the mechanics of the structure at that point. If the mass of the accelerometer is a significant percentage of the effective mass of the structure at the point of attachment, the structure’s frequency response will be altered, resulting in a poor measurement. A simple rule of thumb or exercise to determine if mass loading is a problem is to:
On-Chip Accelerometers Using Bondwire Inertial Sensing
Published in Reza Mahmoudi, Krzysztof Iniewski, Low Power Emerging Wireless Technologies, 2017
Yu-Te Liao, William Biederman, Brian Otis
Many different types of accelerometers exist today, such as piezoelectric, piezoresistive, and capacitive. Each type of accelerometer has different performance characteristics and applications. For example, piezoresistive and piezoelectric accelerometers are usually used as vibration and shock sensing devices due to their high acceleration detection range (>100,000 g) with a bandwidth over 20 kHz [8]. Furthermore, capacitive microelectro-mechanical (MEMS) inertial sensor technology was introduced in the 1980s, allowing a reduction in the sensor size. Analog Devices was the first group to develop a commercial MEMS accelerometer in 1985, which was used for an air bag system. Recently, MEMS accelerometers have demonstrated microgravity resolution, high stability, and linearity through force feedback [9–11]. Existing MEMS accelerometers provide high-quality inertial sensing but require complicated sensor fabrication (bulk/surface machining) and packaging at the wafer level. The complex postprocessing required to integrate the MEMS sensor and electronic IC on the same silicon substrate is the major cost limitation of accelerometer manufacturing and constrains the flexibility and the size of the proof mass.
Device Capabilities Leveraged in Apps Location, Magnetometer, Motion Sensor, Touch, and Scanner
Published in Jithesh Sathyan, Anoop Narayanan, Navin Narayan, K V Shibu, A Comprehensive Guide to Enterprise Mobility, 2016
Jithesh Sathyan, Anoop Narayanan, Navin Narayan, K V Shibu
An accelerometer is a device used to measure proper acceleration. Proper acceleration is the acceleration measured relative to free fall. The device obtains acceleration due to motion with respect to the earth, and for this, the acceleration is measured relative to a local inertial frame. The device can measure both the magnitude and the direction of the acceleration. Nowadays, the type of accelerometers used in mobile devices is the microelectromechanical systems (MEMS). It is capable of detecting free fall, motion, and wake-up. It has dedicated programmable interrupt lines. Mobile devices usually use a three-dimensional (3D) accelerometer capable of 360° motion sensing, which can be controlled by a software. iPhone uses the LIS331DL MEMS chip for acceleration. It measures acceleration in the range 2—8 g and has shock survivability up to 10,000 g per 0.1 s. Accelerometers are commonly used in modern personal electronic devices such as smart phones, personal digital assistants (PDAs), and digital audio players, tablet PCs, digital cameras, advanced video game consoles such as X-Box and PlayStation. It is mainly used as a motion sensor to rotate the screen in the portrait and landscape modes based on the position in which the device is held. It is used for recognizing tap gestures in the screen or on any part of the device. The accelerometer should be calibrated for optimal use. Usually, the devices will be provided with a calibration button, which when pressed will record new acceleration values. The recorded values are taken as reference for further acceleration inputs and finally normalized for optimum results.
FRP-laminated Rubber Isolator: Theoretical Study and Shake Table Test on Isolated Building
Published in Journal of Earthquake Engineering, 2023
Di Wu, Solomon Tesfamariam, Yan Xiong
The instrumentation used in tests mainly include the accelerometer, displacement meter, the laser displacement meter, and the force sensor, which are used to evaluate the dynamic response of the isolated structure and the mechanical properties of the isolators. The type 4381 acceleration/displacement meter produced by the B&K Company is used to measure the seismic responses of the structure in this test. The sensor is a piezoelectric charge accelerometer with high sensitivity and low sensitivity to environmental factors. The frequency range of the accelerometer is from 0.1 to 4800 Hz, and the sensitivity is 98 ± 2% pC/g during the operating frequency range. The acceleration and displacement sensors are placed on each floor to measure each floor acceleration and displacement of the upper structure, respectively. The arrangement of the acceleration and displacement sensors on the different floor is shown in Fig. 12(a). The horizontal deformations of the isolators have been measured and examined by the laser displacement meter fixed between the isolation layer and the shaking table as shown in Fig. 12(b).
Monitoring structural responses during load testing of reinforced concrete bridges: a review
Published in Structure and Infrastructure Engineering, 2022
Gabriela Irene Zarate Garnica, Eva Olivia Leontien Lantsoght, Yuguang Yang
Accelerometers are sensors that measure the acceleration of a structure on one, two, or three axes. There are different types: force-balance, capacitive, piezoresistive, and piezoelectric inclinometers. The piezoelectric accelerometers are the most common type. They are designed to produce an electrical signal proportional to the forces induced by the vibration of the structure (Ettouney & Alampalli, 2012). Quartz and lead zirconate titanate (PZT) are common materials used to output the electrical charge when they are placed under acceleration. A scheme of this type of sensor is shown in Figure 11. The resolution of the measurements can be up to 0.0001 g (PCB, 2011). The advantages of piezoelectric accelerometers are that they are widely commercialized, low cost, and easy to install. However, the interpretation of the measurements for the analysis of structural dynamic can be complex.
Inter-unit reliability of IMU Step metrics using IMeasureU Blue Trident inertial measurement units for running-based team sport tasks
Published in Journal of Sports Sciences, 2021
Mark Armitage, Marco Beato, Stuart A. McErlain-Naylor
Data were collected using IMeasureU Blue Trident inertial measurement units (Vicon Motion Systems Ltd, Oxford, UK). Each unit (42 x 27 × 11 mm, 9.5 grams) incorporates two tri-axial accelerometers: one with a range of ± 16 g (1125 Hz; 16 bit resolution) to provide resolution at lower accelerations; and one with a range of ± 200 g (1600 Hz; 13 bit resolution) which is used when the first accelerometer’s range is exceeded. Two IMeasureU Blue Trident units were affixed to the right distal anteromedial shank of each participant using the provided manufacturer’s straps, ensuring a tight but comfortable fit (Rice et al., 2018). The first unit was positioned 20 mm proximal to the superior aspect of the medial malleolus, the mean of two previously reported positions (Rice et al., 2018; Sheerin et al., 2020). The second unit was placed superior to the first unit (Figure 1), positioned as close as possible without causing inter-unit contact during the tasks. Units were randomly allocated.