Capacitance transducer

Bhushan, B., Kulkami, A.V., Bonin, W. and Wyrobek, J.T., Nanoindentation and picoin dentation measurements using a capacitive transducer system in atomic force microscopy. Philos. Mag. A Phys. Condens. Matter Struct. Defects Mech. Prop., 74(5), 1117-1128 (1996). 

Nanoindentations were carried out by using a commercial AFM (AutoProbe CP Research, Park Scientific Instruments) equipped with a commercial capacitance transducer (TriboScope, Hysitron) with a three-sided pyramidal dia-... 

Other, similar methods for measuring surface-surface interactions, which come under the generic heading of surface force apparatus, include the crossed-filament method. This utilizes a beam deflection technique similar to that now being used in some AFMs for the measurement of surface displacement [94]. Another technique for displacement measurement used in a similar SFA is that of a capacitance transducer. Both techniques suffer the criticism that separation is not measured at the point of interest, i.e., the gap between the two surfaces as measured in the FECO technique. 

Fig. 16.1. Capacitive transducer for resonant gravitational waves detectors.

Interaction parameters for polymer blends, 20 322 in surfactant adsorption, 24 138 Interaortic balloon pump, 3 746 Intercalated disks, myocardium, 5 79 Intercalate hybrid materials, 13 546-548 Intercalation adducts, 13 536-537 Intercalation compounds, 12 777 Intercritical annealing, 23 298 Interdiffusion, 26 772 Interdigitated electrode capacitance transducer, 14 155 Interesterification, 10 811—813, 831 Interest expense, 9 539 Interface chemistry, in foams, 12 3—19 Interface metallurgy materials, 17 834 Interfaces defined, 24 71... 

Elastic elements such as diaphragms and capsules are used as sensing elements in combination with different displacement transducers (e.g. inductive, potentiometric, etc.) for low/medium vacuum measurements down to about 1 torr. Elastic elements have been employed in conjunction with capacitive transducers for the measurement of pressures as low as 10 5 torr. 

The use of capacitance measurement is based upon the principle that the concentration changes as particles settle through a suspension and will alter the effective dielectric constant between the sensing electrodes. A complete capacitance transducer consists of capacitance sensing electrodes together with capacitance sensing electronics, which is essentially a capacitance to voltage converter. 

The resonance method is useful when the data are required at only one frequency or at a small number of frequencies. In a typical device used to measure the dynamic tensile storage modulus, the rod, which has a circular or rectangular cross section, is hung by threads at nodal points. An oscillating force is applied at one end of the rod by means of a piezolectric transducer. The response is detected at the other end by a capacitive transducer. To achieve that, it is very convenient to paint the extremities of the rod in front of the transducers with cooloidal silver or another conductive paint. 

Fig. 6.1.2 Electrical equivalent circuit for a single-ended parallel-plate capacitive transducer interface...

First receptor-based biosensor acetylcholine receptor on a capacitance transducer for cholinetgics [19]... 

Linkage of recombinant HIV proteins to a capacitance transducer by glutaraldehyde coupling to amino-terminated silanes HIV antibody [7]... 

Semiconducting polymers arrays on a chemiresist (capacitance) transducer... 

Enzyme immunoassays on chemiresist (capacitance) transducers Enzyme electrode... 

Strong ZA, Wang AW, McConaghy CF (2002) Hydrogel-actuated capacitive transducer for wireless biosensors. Biomed Microdevices 4(2) 97-103 Thevenot DR, Toth K, Durst RA, Wilson GS (2001) Electrochemical biosensors recommended definitions and classification. Biosens Bioelectron 16(1-2) 121-131 Tirrell M, Kokkoli E, Biesalski M (2002) The role of surface science in bioengineered materials. Surf Sci 500 61-83... 

In Appendix 11A we found that simple manometers, externally mounted level indicators, variable capacitance transducers, and pneumatic valves exhibit inherent second-order dynamic behavior. Design all the systems above so that they exhibit underdamped behavior with a decay ratio equal to. In other words, find the conditions that the values of the physical parameters of these systems should satisfy in order for the device to exhibit underdamped behavior with decay ratio... 

The scheme of such a metal-arch capacitance transducer is shown in Fig. 50. The transducer is about 3 mm thick and has a diameter between 6 and 10 mm. The fixed electrode consists of a sputtered tantalum film on a glass substrate, the dielectric is a reactively sputtered tantalum pentoxide film, and the variable electrode consists of phosphor bronze and is either an arch shaped 15 pm thin foil obtained from a metal strip or a spherical dome shaped foil made by sputtering [245]. A maximum capacitance value of 340 pF could be obtained and short time and long time stability s were better than 0.2 pF min 1 and 0.05 pF hour 1 respectively. The sensitivity of such transducers was between 2000 and 8000 pF mm 1. Q factors have been obtained in... 

Schematic representation of a metal-arch capacitance transducer according to Jones et al. [245]. This capacitance transducer is of the variable-area electrode type. A tantalum/tantalum oxide film structure is deposited onto a flat glass substrate to obtain a suitably flat surface for contact with a flexible electrode which may be a thin metal foil possibly deposited in the shape of a dome or an arch...

Ozturk Z. Z., Zhou R., Weimar U., Ahsen V., Bekarogju O., and Gdpel W., Soluble phthalocyanines for the detection of organic solvents Thin film structures with quartz microbalance and capacitance transducers. Sens. Actuators B, 26-27, 208-212, 1995. 

The third way that a variable capacitance transducer can measure displacement is by having a fixed parallel plate capacitor with a slab of dielectric material having a dielectric constant different from that of air that can slide between the plates (Figure 2.1d). The effective dielectric constant for the capacitor will depend on how much of the slab is between the plates and how much of the region between the plates is occupied only by air. This, also, can yield a transducer with linear capacitance as a function of displacement characteristics. 

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