China
Africa
Explore chapters and articles related to this topic
Model Linearization
Published in Clarence W. de Silva, Modeling of Dynamic Systems with Engineering Applications, 2023
A bridge circuit is commonly used in applications of instrumentation, to make some form of measurement. Typical measurements include change in resistance, change in inductance, change in capacitance (or, generally, change in impedance), oscillating frequency, or some variable (stimulus) that causes these changes. There are many types of bridge circuits. Figure 4.16a shows a Wheatstone bridge. It is a resistance bridge with a constant dc voltage supply (i.e., it is a constant-voltage resistance bridge). A Wheatstone bridge is particularly useful in strain-gage measurements, and consequently in force, torque, and tactile sensors that employ strain-gage techniques. Since a Wheatstone bridge is used primarily in the measurement of small changes in resistance, it could be used in other types of sensing applications as well. For example, in resistance temperature detectors (RTDs), the change in resistance in a metallic (e.g., platinum) element, as caused by a change in temperature, is measured using a bridge circuit.
Conventional Pressure Sensors
Published in J G Webster, Prevention of Pressure Sores, 2019
Most semiconductor strain gage sensors are made by diffusing resistors on the surface of a thin diaphragm. The diaphragm, typically formed by electrochemical etching, is on the order of 10 μm thick and 500 μm in diameter (Esashi et al 1982). As pressure is applied, the diaphragm deflects and the resistance values change accordingly. Diaphragm thickness directly affects the sensitivity of the sensor. Four resistors are typically used in a Wheatstone bridge arrangement. The transverse voltage sensor, developed by Motorola, is a unique four-terminal device which uses a single resistive element, eliminating the need for closely matched resistors (Derrington et al 1982). Guckel’s pill box is similar to a diaphragm sensor, but lateral etching techniques are employed for very small diaphragm sizes on the order of 100 μm by 100 μm (Guckel and Burns 1984).
Sensor Technology
Published in Stephen Horan, Introduction to PCM Telemetering Systems, 2018
One basic technique for measuring pressure, strain, and force is to use a strain gauge or a resistor that changes its resistance in response to a deformation imposed by an agent that acts upon it in the environment. Strain gauge varieties are packaged in single gauge or multigauge configurations.10,11,13,14 The basic parts of a single gauge device are illustrated in Figure 2.6. The operating principle is to deform a wire that has a well defined resistance by the application of an external stimulus. The external force causes a change in the resistance that can be measured, usually by sensing a voltage drop across the gauge. Typically, a Wheatstone bridge is used to precisely measure the change in resistance through a voltage change across the circuit.
Experimental investigation of solar evacuated tube collector with multi-walled carbon nanotube-water-based nanofluid
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Raju Thota, Agnimitra Biswas, Biplab Das, Anal Ranjan Sengupta
Here thermal conductivity and zeta potential of MWCNT-water-based nanofluids are evaluated. Electric charge at the shear plane on the surface of the nanoparticles is known as zeta potential. The KD2 probe, which relies on the transient hot wire (THW) approach (Kumar and Kaushal 2020), is used to enumerate the thermal conductivity of the prepared nanofluid in the range 0.02–2.00 W/m-K, with an accuracy of 0.01 W/m-K. In the THW method, an infinitely long and thin wire (length 0.8 m) is used as a heat source, which is heated electrically. The wire submerged in the liquid provides a constant heat flux. The wire dissipates heat, causing the wire temperature to vary over time. To measure a change in resistance, the Wheatstone bridge circuit is used. Finally, the value of thermal conductivity of the nanofluid based on a change in temperature slope with logarithmic time heating is calculated.
Designing instrumented walker to measure upper-extremity’s efforts: A case study
Published in Assistive Technology, 2019
Mohammad Khodadadi, Mina Arab Baniasad, Mokhtar Arazpour, Farzam Farahmand, Hassan Zohoor
The advantage of fabricating an independent loadcell rather than installing strain gauges on the shafts of the walker is that strain gauge installation on a flat surface is so easier and has less installation error compared to installation on a circular shaft of walkers (measurementsgroup, 2001). Based on an idea from a previous study (Sommer, 2011), it is found out that by making some holes in the loadcell core, strain values will be increased. Furthermore, the loadcells were made of aluminum alloys to provide an appropriate heat transfer (measurementsgroup, 2001). A collection of 350-ohms-straingauges (Tokyo Sokki Kenkyujo Co., Ltd.) were installed on the loadcell core where the thickness is less and strain values are higher. The method and arrangement of installation of the strain gauges to measure axial force (two perpendicular strain gauges on each side of the loadcell core) and shear force (two 45 degree oriented strain gauges on each side of the loadcell core) were based on a technical source (Hoffmann, 2012). Strain gauges were installed in the full-bridge type of Wheatstone bridge (using four strain gauges for measuring each force) so that it has a linear relation between strain and output voltage and has the ability to compensate the temperature errors in measuring strains (measurementsgroup, 2001). The designed loadcell is as Figure 1 (c).
Resilient modulus estimation using in-situ modulus detector: performance and factors
Published in International Journal of Pavement Engineering, 2022
Sang Yeob Kim, Dong-Ju Kim, Jong-Sub Lee, Thomas H.-K. Kang, Yong-Hoon Byun
In this study, an IMD with various types of tip modules was developed to provide a resilient modulus profile of the subgrade. Figure 1 shows the shape of an IMD, which is composed of a tip module, hammer system, and driving rod. To investigate the effect of tip shape on resilient modulus estimation, three tip types were designed: flat, wedge, and cone, each with a diameter of 30 mm. To measure the dynamic force and displacement, four strain gauges and an accelerometer were installed at the tip module. The strain gauges were configured as a Wheatstone bridge circuit, which has been widely used for load cells owing to temperature compensation and bending effect minimisation (Byun and Lee 2013, Kim and Lee 2020). The load cell was calibrated to evaluate the force based on the output voltage measured at the tip module (Hong et al. 2022). To estimate the displacement, a piezoelectric accelerometer (PCB 350C03) with a maximum amplitude of 10,000 g was mounted on the tip module. The dynamic responses from the tip module were recorded and stored on a computer using a data logger at a sampling rate of 10 kHz. The hammer system comprised a hammer, guide, buffer, and anvil. The 43-N hammer and 685-mm-high guide were used to vary the potential energy of the hammer. The buffer and anvil were located between the guide and driving rod to transfer energy to the tip module, apply dynamic loads to subgrade, and minimise high-frequency noise in the force and acceleration signals. The length of the driving rod (1,000 mm) was the same as that of the DCP. The inner and outer diameters of the driving rod were 16 and 24 mm, respectively. Considering the difference in the diameters of the tip module and driving rod, side friction along the driving rod during penetration was negligible.