# Piezometer

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## piezometer

[‚pē·ə′zäm·əd·ər]
(engineering)
An instrument for measuring fluid pressure, such as a gage attached to a pipe containing a gas or liquid.
An instrument for measuring the compressibility of materials, such as a vessel that determines the change in volume of a substance in response to hydrostatic pressure.

## Piezometer

a device used to measure the change in volume of substances that occurs as a result of hydrostatic pressure. Piezometric measurements are used to obtain data on the compressibility, or volume elasticity, of substances and to investigate phase diagrams, phase transitions, and other physical and chemical processes.

The design of piezometers is determined by the range of pressures and temperatures to be applied, by the state of aggregation of the substance to be investigated (gaseous, liquid, or solid), and by the compressibility of the substance. There are two main types of piezometers. In those of the first type, the mass M of the substance being investigated is constant, but its volume V changes with pressure ρ and temperature T. Such piezometers are thick-walled vessels in which pressure is applied to solids, liquids, or gases in order to determine their compressibility. During the experiment, the relationship between the change in V and that in ρ is measured; the temperature of the substance is usually kept constant. In piezometers of the second type, M is a variable quantity, and the volume of the vessel containing the substance to be studied is constant. Here, an allowance must be made for any deformation in the piezometers caused by the application of pressure. Piezometers of the second type are not used in the study of liquids with high viscosity or of solids. In working with such piezometers, p is measured and each change in M is determined either by weighing or, after removal of the load, by such methods as measuring the volume of the discharged gas under standard conditions.

Plunger- or piston-type piezometers are used for determining the compressibility of liquids and solids at pressures in the high range of 108-1010 newtons per square meter (N/m2). During the process of compression, the volume V is determined by noting, either optically or with the aid of electric sensors mounted inside the vessel, the piston’s displacement; a value for ρ is arrived at by measuring the force applied to the piston or by resorting to electric sensors. In a number of cases, the substance under investigation itself serves as a pressure-transmitting medium. For the pressure range ρ ≳ 109-1010 N/m2 (10–100 kilobars), compressibility is determined by other methods, such as X-ray structural analysis. The change in the linear dimensions of bodies acted upon by hydrostatic pressure is measured by linear piezometers.

The term “piezometer” was introduced during the 1820’s in connection with the work done by the British physicist J. Perkins and by H. C. Oersted on the compressibility of liquids. At that time, the piezometer was a vessel that contained the liquid to be investigated. The open end of this vessel was immersed in mercury, which in turn was located at the bottom of a high-pressure vessel. If pressure was applied above the mercury by, for example, water or oil, the mercury would be displaced into the vessel containing the liquid under investigation. The height of the mercury’s rise, which depended both on the applied pressure and the compressibility of the liquid being studied, was recorded visually (in glass piezometers) and by using such means as measuring the resistance change in a platinum wire. Further development of piezometers during the 19th century is associated with the Russian scientists G. F. Parrot, E. Kh. Lents (H. F. E. Lenz), and D. I. Mendeleev and the French physicists E. Amagat and H. V. Regnault; in the 20th century major contributions were made by G. Tammann and the American physicists T. Richards and P. Bridgman.

In the technology of physical experiments at high pressures, the term “piezometer” sometimes denotes thick-walled, high-pressure vessels with a cylindrical channel that are not designed for measurements of compressibility. In English reference sources, the term is also applied to devices used to measure pressures found in flow systems, in the bore of artillery pieces, and at ocean depths.

### REFERENCES

Bridgman, P. W. Fizika vysokikh davlenii. Moscow-Leningrad, 1935. (Translated from English.)
Bridgman, P. W. Noveishie raboty v oblasti vysokikh davlenii. Moscow, 1948. (Translated from English.)
Tsiklis, D. S. Tekhnika fiziko-khimicheskikh issledovanii pri vysokikh i sverkhvysokikh davleniiakh, 3rd ed. Moscow, 1965.
Kornfel’d, M. “Metody i rezul’taty issledovaniia ob”emnoi uprugosti veshchestva.” Uspekhifizicheskikh nauk, 1954, vol. 54, issue 2.

L. D. LIVSHITS

## piezometer

A device for measuring liquid pressure; used to measure the pore water pressure in soil.
References in periodicals archive ?
A boundary between areas of recharge and discharge is proved mathematically, and the anomalies of piezometric surface are explain for the occurrence high permeability shapes of lenses.
For the piezometric tube level at a specific measuring point during a certain period of time, the hysteretic days [x.
The minimum, mean, maximum and standard deviation of piezometric head data in the second group of piezometers are presented in Table 8.
The high groundwater level observed in March via piezometric monitoring was synchronous with maximum soil salinity.
As the piezometric level depends on the operation of Siauliai waterworks, two variants were modelled: with the natural and dropped water levels in the Upper Permian aquifer.
Pressure taps arrayed in a piezometric ring were mounted on the rigid steel ducts in order to obtain an auxiliary measure of the pressure loss across the entire length of the fabric duct.
In situ" test are the most eloquent ones and can be made by piezometric drills enhanced with Cassagrande cells.
5 m above the level of burner was equipped with a 3-way cock and a piezometric tube to measure the fuel consumption from time to time during the operation for consistent values of fuel consumption
Salts present are likely to have collected and concentrated in the drainage zones from upslope areas, or preferentially seeped from below in saline groundwaters under the influence of piezometric pressure of a confined aquifer.
Figure 3 shows unsaturated and saturated zones defined by water table or piezometric levels.
A groundwater level of an unconfined aquifer or the piezometric surface of a confined aquifer indicates the elevations of the atmospheric pressure on the aquifer and hydraulic gradient of the area.
Seventeen piezometric monitoring wells (shown in figure 1) were installed prior to buffer installation as described by Tomer and Burkart (2003) and sampled as described below.

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