Technology & Engineering
Manometer
A manometer is a device used to measure pressure, typically in a closed system. It consists of a U-shaped tube filled with a liquid, with one end connected to the system being measured. The difference in liquid levels in the two arms of the U-tube indicates the pressure in the system.
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12 Key excerpts on "Manometer"
eBook - PDFFluid and Particle Mechanics
Chemical Engineering Division
- S. J. Michell, M. Perry(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
Their common feature is that they measure flow in terms of such quantities as kinetic energy, inertia, specific heat, or some other charac-53 54 FLUID AND PARTICLE MECHANICS teristic quantities. In an important class of meters of this type, the rate of flow is determined from measurement of the differential pressure created in the primary element of the meter. Since the successful operation of these meters largely depends on the accuracy in measuring the differential pressure and on its subsequent interpretation, this subject will be con-sidered first in the following paragraphs. 2.2. Manometers Devices which are used for the measurement of pressure difference between two points of a system are known as Manometers. If one of the points is open to the atmosphere, the difference measured is the gauge pressure and the Manometer measuring this difference is called a pressure gauge. If the measured pressure is that of the atmosphere, the Manometer is called a barometer. A simple Manometer consists of a U-tube partly filled with a liquid, which is usually called the manometric liquid. If the manometric liquid is to mea-sure the pressure of a liquid as well, the two liquids must be immiscible and the manometric liquid must be the heavier one. Mercury is the most common manometric liquid in use, and water, alcohol, carbon-tetrachlo-ride and some light oils are alternatives. Consider a U-tube Manometer, the ends of which have been connected to two points of a system where the respective pressures are p and ρ + Δρ, as shown in Fig. 2.1. Let h be the observed displacement of the manometric Manometric liquid FIG. 2.1. A simple U-tube Manometer. FLOW MEASUREMENT IN PIPES 55 liquid due to the pressure Δρ in excess of p, then the relationship between Δρ and h is obtained from a balance of pressure heads as follows.
eBook - PDF- E. Ower, R. C. Pankhurst(Authors)
- 2014(Publication Date)
- Pergamon(Publisher)
264. Long-range MicroManometers A useful and robust type of Manometer consists in effect of a flexible U-tube, the lower ends of the two vertical limbs being connected by a length of rubber tubing. One of the limbs remains stationary, the other being raised or lowered, by an amount corresponding to the applied pressure difference, by means of a micrometer screw to which it is attached. Figure 10.6 illustrates a Manometer that utilizes this principle and incorporates some useful features introduced at the University of Toronto. (10) Rotation of the nut supporting the movable limb of the U-tube is prevented by means of a keyway, which engages with a vertical key cut on the right of the vertical supporting standard carrying the head of the micrometer screw. In place of a cup for the moving limb, an inclined glass tube of variable slope is employed, having a horizontal mark etched on it. The zero reading is first established with the liquid meniscus in this tube in coincidence with the fixed mark; when a pressure difference is applied, the 260 MEASUREMENT OF AIR FLOW inclined tube is raised on its nut until the liquid is again in equilibrium at the mark. Complete turns of the micrometer screw are indicated by the pointer moving over the vertical scale, and fractions of a turn are observed on the graduated head. The fixed limb of the U-tube consists of a reservoir of large cross-sectional area in comparison with that of the inclined tube, so that the change in level in the reservoir can be neglected.
Available until 4 Dec |Learn morePrinciples of Chemical Engineering Processes
Material and Energy Balances, Second Edition
- Nayef Ghasem, Redhouane Henda(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
The latter are used for better response and increased sensitivity. A Manometer is a U-shaped device that uses a fluid having greater density than other fluids in the process unit. Manometer operation is based on the fact that hydrostatic pressure at the same level in the same fluid must be the same in each leg. To understand how a Manometer works, we must understand how to determine the hydro-static pressure caused by a mass of a column of fluid. By definition of pressure, P F A mg A Vg A Ahg A gh = = = = = ρ ρ ρ Whenever we need to determine the hydrostatic pressure caused by a mass of fluid, it is simply given by P = ρ gh Gauge pressure is the pressure relative to atmospheric pressure. Gauge pres-sure is positive for pressures above atmospheric pressure, and negative for pressures below it. Atmospheric pressure does add to the pressure in any fluid not enclosed in a rigid container. The total pressure, or absolute pres-sure, is thus the sum of gauge pressure and atmospheric pressure: P P P abs gauge atm = + where P abs is absolute pressure P gauge is gauge pressure P atm is atmospheric pressure 26 Principles of Chemical Engineering Processes Example 1.14 Fundamentals of Pressure Problem Consider the Manometer in Example Figure 1.14.1. If h = 10 in. and the Manometer fluid is mercury ( ρ = 13.6 g/cm 3 ), calculate the gauge pres-sure and absolute pressure (14.7 psia). Solution Known quantities: Manometer fluid is mercury, density of mercury, and change in mercury height, h . Find: The gauge and absolute pressure. Analysis: Absolute pressure is obtained by adding the gauge pressure to atmospheric pressure. Gauge pressure = absolute pressure − atmospheric pressure ρ = 13.6 g/cm 3 (or 13.6 times greater than H 2 O) Th gauge pressure lb in us, ft ft gauge c = = = × ( ) P g g h ρ 13 6 62 4 1 12 3 3 .
No longer available |Learn more- Irving Granet, Maurice Bluestein(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
The effective area increases between 13 and 18 ppm (parts per million)/°F for commonly used materials, and a suitable correction for this effect may also be applied. 1.6.2 Manometer We have already shown that the pressure at the base of a column of liquid is simply a function of the height of the column and the specific weight of the liquid. Therefore, the height of a column of liquid of known specific weight can be and is used to measure pressure and pressure differences. Instruments that utilize this principle are known as Manometers, and the study of these pressure-measuring devices is known as manom-etry. By properly arranging a Manometer and selecting the fluid judiciously, it is possible Test gauge gauge Dead-System Variable portion of system volume Vent valve pressur e Inlet valve weight A tmosphere Movable piston FIGURE 1.18 Pressure volume regulator to compensate for fluid leakage in a dead weight gauge. 37 Fundamental Concepts to measure extremely small pressures, very large pressures, and pressure differences. A simple Manometer is shown in Figure 1.19, where the right arm is exposed to the atmo-sphere while the left arm is connected to the unknown pressure. As shown, the fluid is depressed in the left arm and raised in the right arm until no unbalanced pressure forces remain. It has already been demonstrated that the pressure at a given level in either arm must be the same so that we can select any level as reference and write a relation for the pressure. Actually, it is much easier and more convenient to select the interface between the Manometer fluid and the unknown fluid as a common reference level. In Figure 1.19, the pressure at elevation AA is the same in both arms of the Manometer. Starting with the open Manometer arm (right), we have atmospheric pressure p a acting on the fluid. As one proceeds down the arm, the pressure increases until we arrive at level AA , where the pres-sure is p a + γ h .
eBook - PDFInstrument Technology
Measurement of Pressure, Level, Flow and Temperature
- E. B. Jones(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
The pressure reading is stored in binary coded decimal form for actuation of the digital display unit and other data-processing equipment until the next measuring cycle occurs. 1.3.2. Industrial types of Manometer The simple U tube type of Manometer is usually made of glass and contains the appropriate liquid. For industrial use, it is often more convenient to have the U tube made of some tougher material which is less likely to break in the course of use. The glass is therefore often replaced by steel. When this is done, however, it is no longer possible to read the level of the liquid directly. Thus some device must be adopted to move a pointer outside the tube to indicate the level of the mercury inside. If one side of the tube is open to the atmosphere this is reasonably simple, for a float may be placed on the liquid in the open tube, and this float can actuate the mechanism which moves the pointer. When differential pressures are being measured, as in flow metering, both sides must be sealed and other methods used to transmit the position of the liquia level. In such cases it is often more convenient to use a well type of Manometer rather than a simple U tube. One limb of the U tube is greatly enlarged in comparision with the other limb. When a differential pressure is now applied to the Manometer, the rise of the liquid on one side will not equal the fall on the other side, as it does in the simple U tube. The relative sizes of the rise and fall will depend upon the diameters of the tube and well. This principle is also used in single column gauges (Figure 1.17). Suppose a differential pressure of h mm of mercury is established between the two sides of the Manometer as in Figure 1.18, and suppose the diameters of tube and well are d mm and D mm respectively.
eBook - PDF- D.A. Taylor(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
To express gauge pressure as an absolute value it is therefore necessary to add the atmospheric pressure. A differential pressure is the difference in pressure existing between two points. Various methods of pressure measurement are used. These include the balancing of a column of liquid and the elastic deflection of various elements. 33 34 M E A S U R I N G I N S T R U M E N T S Manometers All Manometers balance the pressure to be measured against a column of liquid. The height of the column of liquid is then a measure of the applied pressure. In its simplest form a U-tube is used, where one end is connected to the pressure source and the other is open to atmosphere. The liquid in the tube will be chosen according to the pressure range required, e.g. water for low pressures and mercury for high pressures. The excess of pressure above atmospheric will be shown as the difference in levels, see Figure 3.1 (a). This instrument therefore measures gauge pressure. Where low pressure readings are required, such as for air pressures, an inclined Manometer may be used, see Figure 3.1(b). The length of measuring scale, and hence the sensitivity, is considerably increased by this arrangement. The mercury barometer is a straight tube type of Manometer. A glass capillary tube is sealed at one end, filled with mercury, and then System Atmospheric pressure pressure Scale h = system pressure (gauge value) System pressure Liquid ( b ) Figure 3.1 Manometers: (top) U-tube Manometer; (bottom) inclined Manometer M E A S U R I N G I N S T R U M E N T S 35 Vacuum -Χ Figure 3.2 Mercury barometer inverted in a small bath of mercury, see Figure 3.2. Almost vacuum conditions exist above the column of liquid, which is supported by atmospheric pressure acting on the mercury in the container. The mercury is actually contained in a leather bag which is surrounded by a bakélite casing.
No longer available |Learn moreVacuum
Fundamental Physics Concept (Concepts and Applications)
- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter- 4 Pressure Measurement The construction of a bourdon tube gauge, construction elements are made of brass Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges . A Manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term Manometer is often used to refer specifically to liquid column hydrostatic instruments. ____________________ WORLD TECHNOLOGIES ____________________ A vacuum gauge is used to measure the pressure in a vacuum—which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10 −11 mbar. Absolute, gauge and differential pressures - zero reference Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measure-ments are made relative to a vacuum or to some other ad hoc reference. When distingui-shing between these zero references, the following terms are used: • Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. • Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. • Differential pressure is the difference in pressure between two points. The zero reference in use is usually implied by context, and these words are only added when clarification is needed.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter- 4 Pressure Measurement The construction of a bourdon tube gauge, construction elements are made of brass Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges . A Manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term Manometer is often used to refer specifically to liquid column hydrostatic instruments. ____________________ WORLD TECHNOLOGIES ____________________ A vacuum gauge is used to measure the pressure in a vacuum—which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10 −11 mbar. Absolute, gauge and differential pressures – zero reference Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used: • Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. • Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. • Differential pressure is the difference in pressure between two points. The zero reference in use is usually implied by context, and these words are only added when clarification is needed.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 7 Pressure Measurement The construction of a bourdon tube gauge, construction elements are made of brass Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges . A Manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term Manometer is often used to refer specifically to liquid column hydrostatic instruments. ________________________ WORLD TECHNOLOGIES ________________________ A vacuum gauge is used to measure the pressure in a vacuum—which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10 −11 mbar. Absolute, gauge and differential pressures - zero reference Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases mea-surements are made relative to a vacuum or to some other ad hoc reference. When distin-guishing between these zero references, the following terms are used: • Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. • Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. • Differential pressure is the difference in pressure between two points. The zero reference in use is usually implied by context, and these words are only added when clarification is needed.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 2 Pressure Measurement The construction of a bourdon tube gauge, construction elements are made of brass Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges . A Manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term Manometer is often used to refer specifically to liquid column hydrostatic instruments. ________________________ WORLD TECHNOLOGIES ________________________ A vacuum gauge is used to measure the pressure in a vacuum—which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10 −11 mbar. Absolute, gauge and differential pressures - zero reference Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases mea-surements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used: • Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. • Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. • Differential pressure is the difference in pressure between two points. The zero reference in use is usually implied by context, and these words are only added when clarification is needed.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 2 Pressure Measurement The construction of a bourdon tube gauge, construction elements are made of brass Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges . A Manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term Manometer is often used to refer specifically to liquid column hydrostatic instruments. ________________________ WORLD TECHNOLOGIES ________________________ A vacuum gauge is used to measure the pressure in a vacuum—which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10 −11 mbar. Absolute, gauge and differential pressures - zero reference Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used: • Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. • Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. • Differential pressure is the difference in pressure between two points. The zero reference in use is usually implied by context, and these words are only added when clarification is needed.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Orange Apple(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 3 Pressure Measurement The construction of a bourdon tube gauge, construction elements are made of brass Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges . ________________________ WORLD TECHNOLOGIES ________________________ A Manometer could also be referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term Manometer is often used to refer specifically to liquid column hydrostatic instruments. A vacuum gauge is used to measure the pressure in a vacuum—which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10 −11 mbar. Absolute, gauge and differential pressures - zero reference Although no pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used: • Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. • Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted. • Differential pressure is the difference in pressure between two points. The zero reference in use is usually implied by context, and these words are only added when clarification is needed.
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