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2, 3 or 4 Front Wire Connection Measurements
This Article will discuss what is 2, 3 or 4 Front Wire Connection Measurements concepts with the addition of discussing the Similarities and differences
2 Wire Front connection / Parallel Plate Electrodes
For the majority of dielectric, conductivity, and impedance material measurements, electrode polarization or contact effects are typically minimal. In such cases, the standard configuration involving the sample material positioned between two parallel plate electrodes is most advantageous.
Parallel Plate Electrodes
This setup is straightforward and enables both reproducible and adaptable sample preparation. However, designing a suitable sample cell to operate across wide ranges of frequency, impedance, and temperature without compromising the wide impedance range and high accuracy is exceptionally demanding.
Parallel Plate Electrodes construction
To address these requirements, HZa: A sample cell equipped with an Interface mounted in the cell head has been developed, it is positioned at the top of the sample electrodes. Consequently, users need not be concerned about artifacts resulting from cell contributions to the measured results.
While HZa is designed for mounting a pair of Parallel Plate Electrodes, HZx interface features The ability to measure in 2 Wire front connection mode and can be connected via BNC terminals to any passive sample cell, or to any impedance device under test.
3 or 4 Front Wire Connection / Electrodes
In a measurement involving a material prepared between two parallel plate electrodes with spacing d, the complex permittivity, conductivity, or impedance is determined from the phase-sensitive measurement of the electrodes’ voltage difference (Vs) and current (Is). This method assumes that the applied voltage Vs uniformly drops within the material, creating a constant electric field E = Vs/d. However, this assumption may not hold true if electrical inhomogeneous layers exist at the electrode-sample interface, leading to a significant voltage drop and thereby reducing the E-field in the sample. Such layers can be created by:
- Accumulation of ions at the electrode for ion conductors (e.g., electrolytes and many liquids such as water, causing electrode polarization).
- Poor electrode-sample contact connections (contact impedance). For low-impedance samples, similar effects may arise from non-negligible impedance contributions of the cables connecting the electrodes and the analyzer’s voltage and current terminals.
In principle, the mentioned effects can be mitigated by using separate electrodes for measuring the sample’s current and voltage. This approach helps suppress interface polarization contributions and minimizes the impact of contact or cable effects on the measured results.
In this setup, the outer two electrodes represent the parallel plates of a standard 2-electrode configuration. Two additional electrodes, such as ring or needle electrodes, are positioned in the inner sample area where no interface effects exist, and the field is homogeneous.
In this setup, the outer two electrodes represent the parallel plates of a standard 2-electrode configuration. Two additional electrodes, such as ring or needle electrodes, are positioned in the inner sample area where no interface effects exist, and the field is homogeneous. If the two voltages are measured by an instrument with high enough input impedance, the current flow into the voltage electrodes will be negligible. Consequently, ions will not accumulate at these electrodes. Moreover, due to the minimal current, contributions from contact or cable impedance will not result in any voltage drop, so the electrical parameters of the material portion between the voltage electrodes can be evaluated without interface polarization contributions and without contact or cable effects from the voltage drop between the voltage electrodes and the current flowing through the outer electrodes.
Omega, Lamda and Zeus boast an input impedance higher than 500TΩ parallel to 1 pF. This represents a significant advancement in broadband three- and four-electrode dielectric, conductivity, and electrochemical impedance measurements. But the 1 pF input capacity may be the same as sample capacity at high frequencies, will influence the measured results. Therefore, three- and four-electrode measurements always necessitate a detailed analysis of the currents flowing into the voltage terminals and the related voltage drop at contacts or electrode interfaces in practice.