Pressure hydrostatic measuring devices

Head Devices A variety of devices utilize hydrostatic head as a measure of level. As in the case of displacer devices, accurate level measurement by hydrostatic head requires an accurate knowledge of the densities of both heavier-phase and lighter-phase fluids. The majority of this class of systems utilize standard-pressure and differential-pressure measuring devices. 

For osmotic drug delivery systems, Eq. (2) is of critical importance. This equation demonstrates that the quantity of water that can pass a semipermeable film is directly proportional to the pressure differential across the film as measured by the difference between the hydrostatic and osmotic pressures. Osmotic delivery systems are generally composed of a solid core formulation coated with a semipermeable film. Included in the core formulation is a quantity of material capable of generating an osmotic pressure differential across the film. When placed in an aqueous environment, water is transported across the film. This transported water in turn builds up a hydrostatic pressure within the device which leads to expulsion of the core material through a suitably placed exit port. 

Liquid level measuring devices are classified into two groups (a) direct method, and (b) inferred method. An example of the direct method is the dipstick in your car which measures the height of the oil in the oil pan. An example of the inferred method is a pressure gauge at the bottom of a tank which measures the hydrostatic head pressure from the height of the liquid. 

Several terms for pressure measuring devices are used interchangeably including transmitters, transducers, gauges, sensors, and manometers. More precisely, a gauge is a self-contained device that converts a force from the process to a mechanical motion of needle or other type of pointer. A manometer is a term reserved for an instrument that measures the hydrostatic head of a liquid and generally operates near atmospheric pressure. A transducer or transmitter combines the sensor with a power supply and a converter— generally mechanical-to-electrical or mechanical-to-pneumatic. The sensor... 

There are static and dynamic methods. The static methods measure the tension of practically stationary surfaces which have been formed for an appreciable time, and depend on one of two principles. The most accurate depend on the pressure difference set up on the two sides of a curved surface possessing surface tension (Chap. I, 10), and are often only devices for the determination of hydrostatic pressure at a prescribed curvature of the liquid these include the capillary height method, with its numerous variants, the maximum bubble pressure method, the drop-weight method, and the method of sessile drops. The second principle, less accurate, but very often convenient because of its rapidity, is the formation of a film of the liquid and its extension by means of a support caused to adhere to the liquid temporarily methods in this class include the detachment of a ring or plate from the surface of any liquid, and the measurement of the tension of soap solutions by extending a film. 

Unfortunately, the use of the terms osmotic pressure and osmotic potential, as well as their algebraic sign, varies in the literature. Osmotic pressures have been measured using an osmometer (Fig. 2-8), a device having a membrane that ideally is permeable to water but not to the solutes present. When pure water is placed on one side of the membrane and some solution on the other, a net diffusion of water occurs toward the side with the solutes. To counteract this tendency and establish equilibrium, a hydrostatic pressure is necessary on the solution side. This pressure is often called the osmotic... 

A very small and specialized use of chemical grouts is for sealing piezometers. These devices, which are placed in drill holes to measure hydrostatic pressures in the formation, must be isolated in the hole to keep them unaffected by pressures in other zones penetrated by the drill hole. Usual procedures make use of bentonite balls or pellets, which swell in the presence of water to seal the drill hole with an impervious mass. The swelling takes time, however—as much as 36 h. The use of chemical grouts with a very rapid setting time can create a seal in seconds. 

C. C. Y. Poon, Y. T. Zhang and Y. B. Liu, Modeling of pulse transit time under the effects of hydrostatic pressure for cuffless blood pressure measurements, in Proceedings of the 3rd lEEE-EMBS International Summer School and Symposium on Medical Devices and Biosensors, U.S.A., pp, 65-68,2006. 

Interior corrosion is best evaluated by a hydrostatic test combined with careful visual inspection. Ultrasonic thickness-measuring and flaw-detection devices may be used to evaluate specific conditions. Corrosion limits for both low and high pressure steel cylinders were dis-... 

Water jacket volumetric expansion is the standard method of testing high pressure cylinders in the compressed gas industries. This method is applicable to all hydrostatic tests when volumetric expansion determinations are required, that is, when expansion, elastic expansion, permanent expansion, and percent permanent expansion measurements are required. It consists of enclosing the cylinder, full of water, in a vessel completely filled with water. The measurement is done with a suitable device, such as a leveling burette, attached to the jacket vessel. This measures the volume of water forced from the jacket upon the application of pressure to the interior of the cylinder, which causes expansion of the cylinder, and the volume remaining displaced upon release of the pressure. These volumes represent the total and permanent expansions of the cylinder, respectively. 

In order to clarify the origins of anomaly in the compression curve of CeAl2, the electrical resistance of CeAl2 was measured up to 23 GPa at room temperature using diamond-anvil cell under quasi-hydrostatic condition. According to the result obtained by cubic-anvil-type pressure device, the p P) increases with increasing pressure up to 5.5 GPa, and then decreases as shown in Figure 19B. The maximum is explained to be due to the Kondo effect, where tiie Kondo temperature Tr (which is around 6 K at ambient pressure) increases with pressure and then reaches room temperature around 5.5 GPa, that is, the pressure-induced crossover occurs in the vicinity of 5.5 GPa at room temperature. 

The coefficients di and 24 associated with shear deformation are seldom used as there are a lack of practical applications using the shear mode. The most important piezoelectric coefficients for determining a material s suitability for a particular device are the d j and g j components and the hydrostatic coefficients dh and The coefficient is a measure of the charge generated owing to the application of a hydrostatic pressure. As the stresses are uniform in all three directions, d is simply... 

---