Manometers electrical

Manufacturing of products containing mercury, e.g., thermometers, manometers, electrical and electronic switches... 

This equation tells us that during the course of a reaction, reactants are consumed while products are formed. We can follow the progress of a reaction by monitoring either the decrease in concentration of the reactants or the increase in the concentrations of the products. The method used to monitor changes in reactant or product concentrations depends on the specific reaction. In a reaction that either consumes or produces a colored species, we can measure the intensity of the color over time with a spectrometer. In a reaction that either consumes or produces a gas, we can measure the change in pressure over time with a manometer. Electrical conductance measurement can be used to monitor the progress if ionic species are consumed or produced. 

Mechanical manometers are the oldest, simplest, and most reliable pressure measurement instruments. They have some disadvantages, which is one reason the use of electrical manometers is expanding. Their simplicity and fundamental nature can, however, be an advantage. 

Electrical manometers have developed during the last 30 years. Modern electrical manometers are well suited for ventilation applications, both in the laboratory and in the field. The advantage of this type of instrument is fhat they are sensitive enough to measure small pressure differences with electrical output, enabling monitoring. A convenient feature, especially in the field is that the instrument is hand-held and there is no need for leveling on a bench, as for fluid manometers. The conversion of the pressure difference into an electrical signal can be based on several different phenomena. 

The second, mechanical and electrical manometers, require more frequent calibration. Changes in the elastic properties of the pressure transducer, wearing in mechanical parts, and electronic circuitry drift influence the properties of the instruments, giving rise to repeated calibration. 

Premier and Schupp have made vapour-density measurements with sulphur enclosed in a quartz bulb heated electrically and connected with a manometer consisting of a spiral of silica tubing attached to a small mirror. The pressure was measured by the amount of unwinding of the spiral. The same method has been used by Bodenstein and Katavama in studving the equilibrium ... 

The high mobility and tendency to dispersion exhibited by mercury, and the ease with which it forms alloys (amalgams) with many laboratory and electrical contact metals, can cause severe corrosion problems in laboratories. A filter-cyclone trap is described to contain completely mercury ejected accidentally by overpressuring of mercury manometers and similar items. 

Figure 4 Schematic of an oxygen uptake device. 1, sample 2, electrical oven 3, Hg manometer 4, intermediate vessel for pressure adjustment 5, drying vessel 6, control thermometer 7, outlet to vacuum pump and 8, inlet for gas feeding. Reproduced with permission from Zaharescu [10]. Springer 2001.

To run it under automated conditions, the bioreactor was equipped with two temperature sensors, two pH electrodes, a water level detector, a manometer and a computer-controlled electric valve. Control of key parameters (pH, temperature, dilution rates) has allowed to define the culture conditions producing maximal amounts of molecular hydrogen. 

Fig. 1. Scheme of apparatus. 1—Discharge tube 2—flask with water 3—nozzle 4—reaction vessel 5—electrical furnace 6—stopcock valve 7—thermocouple 8—trap 9—manometer 10—slides 11—spectrograph slit 12—hydroxyl source 13—discharge tube electrodes 14—transformer 15—vessel of prefixed volume. 

The inner counter cylinder, made of metallized Mylar foil, is leak-tight relative to the outer counter. By means of two solenoid valves actuated by a differential mercury manometer, the outer and inner counters can be filled separately with a pressure differential on the partitioning foil of less than 0.5 cm. Hg. This pressure controller minimizes the danger of rupturing the partition. Two control circuit diagrams are shown in Figure 3. Figure 3A shows the mercury tube with electrical... 

Strain Gages. Essentially, they are based on electrical measurements of strains produced by the action of stress. There are several ways for measuring strains, but the most convenient is the resistance method. The apparatus used for these measurements, known as "resistance manometer , depends upon the change in resistance of a metal (such as platinum, manganin or mercury) when subjected to pressure. The change in resistance is usually measured by means of a very sensitive Wheatstone bridge, but it may also be measured by a potentiometer or by an... 

G. Bourdon Gauges. As an alternative to mercury manometers there is a variety of gauges based on mechanical or electrical pressure transducers. This section presents a description of purely mechanical gauges which still find use in this electronic age.4 The metal Bourdon gauge (Fig. 7.5) is fashioned around a semicircular thin-walled metal tube with mechanical linkage to a pointer. Fused-quartz spiral gauges are also available. In this case, a thin spiral is sensitive to a pressure differential, and the deflection is balanced with air pressure in the surrounding envelope. The air pressure is then measured with a manometer. 

A device for foam dispersity determination by measuring the local foam expansion ratio and the pressure in Plateau borders is illustrated in Fig. 4.4. It consists of a glass container equipped with platinum electrodes and a micromanometer. The container bottom is a porous plate (a sintered glass filter). The pressure Ap is measured with a capillary micromanometer and the expansion ratio is determined by the electrical conductivity of the foam. The manometer and the electrodes are positioned so that to ensure a distance of 1.0-1.5 cm between them and the porous plate. When the distance is small the liquid in the porous... 

You acquire an insulated 2.000-liter container with a known heat capacity and a built-in electrical heating coil that can deliver a known heat input to the contents of the container. A calibrated thermocouple is used to measure the temperature in the vessel, and the pressure is measured with a mercury manometer. 

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