Capacitance meters

Capacitance meters in which the electrical capacitance is a function of the degree of deposition of moisture from the atmosphere. 

The dielectric constant can be used as a criterion for screening, ranking, and selecting demulsifiers for emulsion breaking. In a study, the dielectric constants of emulsions and demulsifiers were measured using a portable capacitance meter, and bottle tests were conducted according to the API specification [18]. The results showed that the dielectric constants can be used effectively to screen and rank demulsifiers, whereas a confirmatory bottle test should be conducted... 

It measures differential pressures. A thin diaphragm separates two chambers (see Fig. 1.28). One of the two chambers is kept at a constant pressure. A pressure difference causes the bending of the diaphragm which forms, together with a fixed electrode, a capacitor. The change in capacitance is measured by a very sensitive capacitance meter (measurement of AC 10 19 Farad are possible). 

The capacitance type essentially measures the dielectric constant of wood. At a given frequency, the dielectric constant increases with wood density, moisture content (Figure 4), and increasing temperature (JO). The most effective electrode configuration for a capacitance meter appears to be a pair of flat parallel electrodes contacting each of two opposite faces of the wood to be measured. There is then... 

Capacitance meters are sensitive to wood density and are harder to calibrate. They have a major advantage in ease of use. The meter need only be laid on the wood and the capacitance measured between two plates that lie side-by-side in a hand-held device. Alternatively meters can be installed with plates on either side of the boards in a production line. 

H. Ren, R. B. Fair, and M. G. Pollack, Automated on-chip droplet dispensing with volume control by electro-wetting actuation and capacitance metering, Sensors and Actuators B-Chemical, vol. 98, no. 2-3, pp. 319-327, Mar. 2004. 

The capacitance meter is balanced and/or read. The specimen is removed and the capacitance reset to the original value by adjusting the micrometer. The permittivity can be calculated from the specimen thickness and micrometer adjustment. The dissipation factor can be calculated from these readings and the initial dissipation factor of the (specimen + electrode) assembly. 

Parallel plate capacitor Capacitance Impedance bridge, capacitance meter Moderate to high Moderate Moderate to large... 

Although specialized instruments such as a separate frequency counter or capacitance meter may be the best choice for a specific range of tasks, combinations of instruments are available for the convenience of maintenance personnel. Separate analyzers usually offer a broader range of measurement capabilities, but a combined instrument often makes field servicing easier. 

Figure 7-13 Auburn International capacitance meter. (Reprinted with permission of Auburn International.)...

The tank was instrumented to provide the pressure and the temperature of both the liquid and vapor at various positions in the tank. The temperatures were obtained both from thermocouples and from wire-wound carbon resistors. Additional instrumentation included a capacitance meter to indicate the liquid level. 

At time zero, the tank filling was completed and the tank vent to sea-level atmosphere was closed. The liquid level indicated by the capacitance meter was about 20 in. from the bottom of the tank at this time. The tank pressure was 15 psia, and the entire liquid was at a uniform temperature of 39 R. The vapor immediately above the liquid surface was about 6 F warmer than the liquid. 

With the liquid level at the three-quarter-full point the capacitance meter was again tuned to resonance and the dial divisions were recorded. This procedure was repeated for each quarter-point and for the 100 gas condition. Knowing the null point readings at the quarter-points permitted the plotting of a curve of volumetric vapor—liquid ratio versus potentiometer dial divisions. 

Electro-Deposited (ED) films were prepared on Indium Tin oxide (ITO) coated slides closely following the procedure described in ref. [7]. ED films were allowed to dry in a constant 12% relative humidity (R.H.) chamber for 24 hrs prior to the completion of the capacitive cell which consisted of vacuum evaporation of 5000 A of polyethalene (PE) and 50 to 90 A of Pt. Typical capacitor areas were from 50 to 80 mm. Capacitances ranged from 600pf to 1,2 nf, as measured with a B K Precision digital capacitance meter. Film thicknesses were measured with a Talysurf apparatus, which probes the film surface with a fine diamond tip coupled to a mechanic-electric transducer. Typical values ranged from 3 to 6 m i ( 40 A). A schematic illustration of a finished capacitor is presented in figure 1. 

The dielectric constants were measured with a YHP 4278 capacitance meter at a frequency of 1 kHz and a temperature of 23 °C. Samples were preconditioned at 1 Torr and 120 °C for 2 h to eliminate adsorbed water. 

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