Capacitive coupling, external

FlO. 6.64. Interference from external sources due to inductive and capacitive coupling... 

P. Kuban and P.C. Hauser, Effects of the cell geometry and operating parameters on the performance of an external contactless conductivity detector for microchip electrophoresis, Lab Chip, 5 (2005) 407-415. J.G.A. Brito-Neto, J.A.F. da Silva, L. Blanes and C.L. do Lago, Understanding capacitively coupled contactless conductivity detection in capillary and microchip electrophoresis. Part 2. Peak shape, stray capacitance, noise, and actual electronics, Electroanalysis, 17 (2005) 1207-1214. 

Because an electrode does not function as electrode in DC or alternating current high-frequency discharge, the electrode system could be kept outside a glass reactor (capacitive external electrodes) or a coil around a glass tube (inductively coupled external electrode) can be used to create plasma. These modes of coupling could be dealt as a factor in the system-dependent aspect of plasma polymerization, i.e., the basic plasma polymerization remains the same. 

The equipment used for plasma polymerization, as well as the basic deposition mechanism, is shown in Fig. 1. Although commercial equipment is available, most researchers choose to design and construct their own equipment. AU that is needed is a vacuum chamber with a pump so that a gas or vapour can flow through the chamber and a means for exciting a plasma. Typically, internal electrodes (capacitively coupled plasma) or external coils are used (inductively coupled plasma), as shown in Fig. 1. The power supply can be DC, AC (60 Hz), RF (12.56 MHz), or microwave frequency (2.35 GHz). During deposition the pressure in the chamber is, typically, of the order of 1-20 Pa and powers of 1-100 W are often used. 

A capacitive coupling between a secondary radio-frequency(rf) channel and the gradient coil of a standard commercially available high resolution NMR spectrometer and probe head is described and used to introduce a low level exponentially damped rf signal near the frequency of the primary rf channel to serve as an external concentration standard, in analogy to the so-called ERETIC (TM) method. 

In capacitively coupled rf discharges, the plasma potential, and hence the sheath potential at the electrodes, can have a time-varying value of tens to hundreds of volts. When the electrodes have a different effective area, the plasma potential can also have a large dc potential with respect to one or more of the electrodes. These factors affect the distribution of ion energies incident on the electrode surfaces in an rf discharge. The electrode potentials can be varied using an external capacitance. 

FIG. 7 Simplified equivalent circuit for charge-transfer processes at externally biased ITIES. The parallel arrangement of double layer capacitance (Cdi), impedance of base electrolyte transfer (Zj,) and electron-transfer impedance (Zf) is coupled in series with the uncompensated resistance (R ) between the reference electrodes. (Reprinted from Ref. 74 with permission from Elsevier Science.)... 

For time t > % this current is zero because the carrier would have reached the substrate. The current I(t) can be detected via the voltage it induces in the external circuit. Shortly, the equivalent electrical circuit of the XTOF experiment under the small-signal condition contains the coupling capacitance Cl (the sum of the amplifier and the parasitic capacitances) and f L ( l is the load resistance). The total current is the sum of the conduction current due to the drift of photogenerated charge and the displacement current and is equal to zero (for further details, see Ref [15]),... 

Figure 4.20 Equivalent circuit for the channeltron/channelplate as the current source i(t) shown together with the main components of the external circuit. CD is the capacitance of the detector which is depicted by the dotted lines in order to indicate that - in contrast to actual electronic components - it is a property inherent to the detector HV is a high voltage source, Ra the load resistor, CK the high voltage coupling capacitor and Amp the...

A persistent question regarding carbon capacitance is related to the relative contributions of Faradaic ( pseudocapacitance ) and non-Faradaic (i.e., double-layer) processes [85,87,95,187], A practical issue that may help resolve the uncertainties regarding DL- and pseudo-capacitance is the relationship between the PZC (or the point of zero potential) [150] and the point of zero charge (or isoelectric point) of carbons [4], The former corresponds to the electrode potential at which the surface charge density is zero. The latter is the pH value for which the zeta potential (or electrophoretic mobility) and the net surface charge is zero. At a more fundamental level (see Figure 5.6), the discussion here focuses on the coupling of an externally imposed double layer (an electrically polarized interface) and a double layer formed spontaneously by preferential adsorp-tion/desorption of ions (an electrically relaxed interface). This issue has been discussed extensively (and authoritatively ) by Lyklema and coworkers [188-191] for amphifunctionally electrified... 

Hyperthermia and thermoablation have been accomplished using capacitive or inductive coupling of rf fields (10-100 MHz), microwaves (> 300 MHz), ultrasound, lasers or external heat [171-177]. Macroscopic metal implants of Cu and other high-conductivity metals have been used to induce eddy-current heating. The absorbed power per mass is called the specific absorption rate (SAR), which can be expressed as... 

The complex electric permittivity, k = k + k , where k = C/C o is the real, and k = tan(8) / K is the complex part of the permittivity, was measured in the frequency interval 300 Hz - 1 MHz at different temperatures by a Solartron 1200 inq>edance gain analyser, using a parallel plate capacitor made of stainless steel. From the capacitance, C, and the tangent loss, tan(6), the values of k and k were calculated [2]. The temperature was controlled within O.IK using a platinum resistor Pt(lOO) as a sensor and a K30 Modinegen external cryostat coupled with a N-180 ultra-cryostat. 

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