Electrode series resistance measurement

The drill collar acts as a series of elongated electrodes in a way similar to the laterolog 3 wireline sonde. The lower electrode, which is the drill bit, is used to get the forward resistivity curve. A lateral resistivity measurement is made between the two toroid receivers. An example of toroid logs is shown in Figure 4-279. 

In three-electrode measnrements, the main source of error at high frequencies is the reference electrode. It is advisable to use a low-impedance reference electrode or a qnasi-reference electrode such as an annealed Pt wire when making EIS measurements above 100 kHz. Lead lengths should be kept to a minimum to minimise stray indnctance and capacitance, and the cell design should be optimised to minimise series resistance losses glass frits used to separate the counter-electrode compartment are a common source of high-frequency artefacts, and these should be avoided. 

Data Analysis. Complex admittance determinations were fitted by an admittance function (13, 14, 16) based on the linearized HH equations (I). Admittance measurements were made under steady-state conditions (see Figures 2 and 4). Series resistance (Rs), the access resistance between the two voltage electrodes and up to the inner and outer surfaces of the axon membrane was not removed from measurements. Instead Rs was included and determined in the fit of the steady-state admittance model to the data. The measured complex admittance, therefore, is... 

When low resistance values (< 10kf2) are being measured, series resistance errors may arise from the leads connecting the electrodes to the "resistance meter" or from the contact resistances between the electrodes and the test material. Both may be eliminated by using "four-electrode" measuring systems where the electrodes and leads used for current and potential connection are completely separate. Obviously, the meter must be one designed for four-terminal measurement and will employ the "fixed current.measured potential" system. 

Although in principle, a four-electrode system may be used to eliminate series resistance (connection) errors, this will rarely be found beneficial in measuring the surface... 

The incorrect determination of illuminated surface area will directly affect measured jsc- Photoelectrons and holes that participate in side reactions such as corrosion, oxygen reduction, or the oxidation of organic contaminants/surfactants can lead to inflated estimates of STH from this technique. Failure to prevent the product of one electrode (H2 or O2) from reaching the complementary electrode (and consequently undergoing the reverse reaction) can inflate the STH. Inadequate calibration of the light source can lead to over or underestimated STH. An electrolyte with low ionic conductivity will reduce y sc by increasing series resistance. 

The ESR results from the Nyquist plots of the impedance spectra could agree well with the values obtained via the IR drop in GCD measurements. For instance, Stoller et al. [30] reported the Nyquist plots for three-type cells packaged cell and two-electrode test cells with two different separators. The real component of impedance of the Nyquist plot (Z-axis) described gradually increased series resistances that were observed from the packaged cell, the two-electrode cell with Celgard separator, and the two-electrode cell with separator from the package. These results are consistent with the values calculated by the IR drop from the GCD curves. 

Tlie series resistance in these models may be regarded as an access resistance to the electrode interface, dependent on electrolyte conductivity and geometry, but not linked to the polarization processes. As such it belongs to the chapter on contact media, and should be subtracted from measured electrode impedance when analyzing polarization immittance. 

The term electrode polarization immittance is sometimes related to the total immittanee of the equivalent circuit of Figure 7.20, but it is sometimes useful to exclude the series resistance Rsoi if it has the character of being an access resistance to the electrode processes. Without electrochemical reaction, measured currents are due to double layer components and sorption. The term electrode polarization immittance should more often either be avoided or defined. The processes involved are of a very different nature, and in a measuring set-up different variables must be controlled dependent on what effects are to be studied. The electrode immittance of an electronic conductor in contact with 0.9% NaCl is of special interest to us. Data for such interfaces are found in Section 7.4. 

Starting with EIS measured with synunetrical gas supply, an equivalent circuit for the complete PEFC can be applied for the simulation of the measured impedance spectra of the PEFC. Besides a series resistance (electrolyte or membrane resistance Red, the equivalent circuit (Figure 4.5.60h) contains three time constants of parallel RIC. In the simulation the capacitance (C) was replaced by CPE (CPE = constant phase element) due to the porous structure of the electrodes. The cathode can be described using a time constant for the charge transfer through the double... 

The technique to be described applies to any electrode that exhibits a high series resistance, but is used mainly for experimental determination of the series resistance of glass micropipettes. Techniques have been described in the literature which use both constant-voltage and constant-current methods under dc or pulse conditions (Frank and Becker, 1964 Geddes, 1972). For dc measurements, provision is made for balancing out the tip potential of a glass micropipette. 

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