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Calorimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Larry A. DeWerd, Blake R. Smith
Graphite calorimeters have also taken on more compact forms and streamline operation. Contemporary graphite and water calorimeters are very fragile, cumbersome, and require specialized equipment and experience to perform a successful measurement. Probe calorimeters have been proposed and shown as a potential integration of absolute graphite dosimetry, which can be performed at a clinic using the resources conventionally available to a medical physicist [5]. The proposed instrument has been operated using both adiabatic and isothermal modes. A Wheatstone bridge is built into the detector electronics, which relates a voltage difference measured using a voltmeter. An illustration of a graphite probe for MV dosimetry is shown in Figure 3.4.
Infertility Diagnosis and Treatment
Published in Sujoy K. Guba, Bioengineering in Reproductive Medicine, 2020
Later technology abandoned the volume assessment approach and focused on monitoring the penile girth or the diameter. Karacan47 devised a simple transducer comprising of an elastic silicone rubber tubing filled with mercury and having platinum electrodes at the two ends in contact with the mercury. The tubing encircled the penis with the ends of the tube tied together with a short length of string (Figure 4.12). The resistance (R) between the platinum electrodes is given by R = ρ1/a, where ρ is the specific resistance of mercury, 1 the circumferential length between the electrodes and a the crossectional area of the mercury column within the tube. With penile expansion the tubing distends resulting in an increase in the length 1 and a reduction in the area a. Both these changes increase the resistance R which is measured by means of a Wheatstone bridge. Unbalanced output voltage of the bridge can be recorded to give a graph of penile expansion. Advantage of the transducer over the volume measuring devices is that it is small in size and unobstrusive and so can be used without significantly affecting the psychology of the individual. A disadvantage is that once the penile diameter falls below the relaxed size of the silicone rubber loop no further data is obtained. If the loop is made small so as to closely fit the smallest penile size, excessive constricting force is exerted on the penis when there is erection.
Conventional Pressure Sensors
Published in J G Webster, Prevention of Pressure Sores, 2019
The dimensional changes and piezoresistive effect are very small, so the gage factor of metal strain gages is significantly less than that of semiconductor devices. An advantage of metal strain gages is that their response is nearly linear, although they have a significant temperature dependence. A Wheatstone bridge is generally used with metal strain gages to sense small changes in resistance. The bridge also helps reduce problems due to temperature changes, but matching the resistance values precisely can be expensive.
Development of a nitinol-actuated surgical instrument for laparoscopic renal denervation: feasibility test in a swine survival model
Published in International Journal of Hyperthermia, 2020
Donghyun Yim, Jinhwan Baik, Sangyong Lee, Sunchoel Yang, Chang Wook Jeong, Sung-Min Park
In strain tests, three-wire, pre-wired, and quarter-bridge SGs (KFH-06-120-D16-11L1M2S, Omega Engineering, Stamford, CT, USA) were attached over the bending surface of nitinol using cyanoacrylate adhesive (Z70, HBM, Darmstadt, Germany). Following excitation from a DC power supply (PWS4305, Tektronix, Beaverton, OR, USA) at 5 V, which is below the module’s maximum excitation voltage of 10 V, output voltage was measured using a 6-1/2 digit precision multimeter (DMM-4040, Tektronix, Beaverton, OR, USA). To detect small strain in the order of a few milli-strain, many SG circuit configurations include a Wheatstone bridge. Therefore, a SG, a power supply, and a multimeter were connected to a Wheatstone bridge completion module (BCM-1, Omega Engineering, Stamford, CT, USA) using screw terminals (Figure 2(a–c)).
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
One of the main contributions of this study is reducing the price and weight of the instrumentation. Both the weight and the price of the designed loadcell are roughly ¼ of a commercial bidirectional loadcell’s weight and price while comparing with 6-axis loadcells, this price is negligible. In addition, the custom-made electronic board can provide more than 1 circuit (4 circuits are used in this study) for measuring and amplifying the Wheatstone bridge with a low price. The weight of the walker without instrumentation is about 3 kg. After instrumentation with loadcells and the electronic board, it has about 4 kg weight. There are few studies which aim to analyze the upper-extremity’s efforts in the walker while a lot of studies are about crutches. Moreover, a comprehensive analysis of upper-extremities for measuring forces and moments applied to all three major upper-extremity’s joints including wrist, elbow and shoulder in all three directions in using walker has not seen in the literature.
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
The majority of implantable sensors for orthopedics are designed for monitoring mechanical parameters such as force loading at the implant site or stress/strain on the implant. Most of these implants are instrumented with strain gauges [29,50,60], which are commonly used to measure the stress or strain on an object. Strain gauges are electrical components that change their resistance in response to mechanical strain. As illustrated in Figure 1, a Wheatstone bridge circuit is typically used to convert the strain gauge’s resistance to voltage so the signal can be digitally processed. Strain gauges are popular for orthopedic implants because they are a mature technology, relatively robust, and have good sensitivity to an applied strain. They are also easy to incorporate into orthopedic implants without significantly disturbing the implant integrity [19,37]. Many earlier strain gauge implantable sensors [20] relied on transcutaneous wired connections to external electronics for data collection [61]. Today, however, many strain gauge implants have wireless telemetry (see Figure 1), which significantly improves their clinical utility due to conveniences in data gathering and significant reduction in infections [62]. In addition to strain gauges, other novel sensor technologies have also been developed for various orthopedic applications. For example, researchers have developed carbon nanotube-based sensors for monitoring tissue growth at the implant tissue interface [63], and capacitive sensors for detecting infections [64]. While these sensing technologies have shown promising results in vitro, they have not yet been implemented into implantable systems for in vivo or clinical orthopedic applications.