Effect of Shielding and Dummy Plates for Electro Static Capacity of Air Capacitor with Long Distance Parallel Plates

Abstract

We are investigating a non-invasive measurement method of the temperature in a head in terms of the temperature dependency of its permittivity. We have to get the method that an electro static capacity of capacitor with long distance is measured precisely. The capacitor is composed of a pair of the measurement plates mounted on a head. However the above approach is virtually very difficult because of the fringing of the electric fields at the extremities and the system shielding.To realize the present research, we are now studying the measurement method of an air capacitor composed of a pair of small parallel plates and a pair of additional plates called dummy, where the distance between the small plates is long and the electric potential of each dummy electrode is equal to that of each measurement plate. In this paper are described the effects of dummy plates and shielding, and is discussed a feasibility of non-invasive measurement method of the temperature in the head. The experiment resulted in that the concern with a shielding and a fringe of plates when the length between the inner edge and the outer edge of the dummy plate amounted to about twice the distance between both measurement plates.

Estimation of the location of dielectrics using a capacitor with widely spaced parallel electrodes and additional electrodes

“…2(b), that is, the distance from the end of the measuring electrode to the end of the additional electrode, is equal to the distance d between the measuring electrodes (as explained in Ref. 2). The dielectrics (acrylic rods) used in the experiments had a cross section of 10 × 10 mm and a length of 170 mm, as shown in Fig.…”

“…The authors previously studied the accurate measurement of small electrostatic capacitances by using widely spaced parallel-plate capacitors [2]. When the distance between the measuring electrodes is long with respect to the side of the square electrode, the electrostatic capacitance becomes very small, and in addition, electrode end effects become pronounced and the electric field between the measuring electrodes becomes nonuniform.…”

“…When the distance between the measuring electrodes is long with respect to the side of the square electrode, the electrostatic capacitance becomes very small, and in addition, electrode end effects become pronounced and the electric field between the measuring electrodes becomes nonuniform. As a solution to this problem, we proposed a method for accurate measurement of the electrostatic capacitance between electrodes, without the influence of disturbances or stray capacitance: specifically, we used a three-terminal capacitor with a shield that has the same potential as the low-potential measuring electrode to which an ammeter is connected [2].…”

Signal processing for brain temperature change detection by noninvasive measurement: An independent component analysis approach

“…The end-goal of this research is to establish technology for measuring brain temperature distributions using noninvasive techniques. Methods proposed before treat the biological tissue as a dielectric, and measure the dielectric constant by sandwiching the brain between long-distance parallel plate electrodes [8,9]. The measurement principles are shown in Fig.…”

“…2, February 2004, pp. 673-682 temperature changes that make use of the temperature dependence of the relative permittivity of the brain [8][9][10][11]. The latter methods in particular are extremely significant from the viewpoint of ease of the measurement apparatus.…”