The instruments for measuring pressure They are devices of different materials that have an element that changes in some way when subjected to pressure. This change is recorded on a calibrated scale or screen, and is expressed in units of pressure..
The units of measure in which pressure is expressed indicate a unit of force over a unit of area.
Although the standard unit of measurement is Pascal (N / m2), it is also measured in pounds per square inch (PSI), in atmospheres (atm), in kilograms per square centimeters (kg / cm2), inches of mercury (Hg) and millimeters of mercury (mm Hg).
In other words, pressure is force per unit area. It is experienced when that force is perpendicular to the surface.
The different types of pressure are:
There are several instruments to measure pressure and, although most are used to measure relative pressure, there are some designed to measure absolute pressure..
It is also known as a two-branch open manometer. This is a device used to measure the pressure difference between two places.
The fluid used by the differential manometer to indicate the values can be any liquid: water, kerosene, alcohol, among others. The essential condition is that it does not mix with the fluid that is under pressure.
In case you are trying to measure high pressures or very large pressure differences, the liquid should be very dense. In these cases, mercury is usually used.
In a manometer the measurements can go from 0 to 0.5 KPa (≈ 0.2 ”H2O); or from 0 to 7000 KPa (≈ 1000 psi).
It is a type of manometer that is used to measure small gaseous pressures. Measures absolute pressures and has branches shorter than the differential.
It is a device that is used to measure the vacuum; that is, to measure pressures below atmospheric pressure.
It turns out to be a very useful tool in cold plants or where liquefied gases are worked, because the critical points of gases and steam are calculated based on absolute temperatures and pressures..
Although the measurement range depends on the material from which it is made, it can cover measurements between -0.5 and 0 KPa; and from -100 to 0 KPa (≈ -30 to 0 “Hg).
Some of the types of vacuum gauges are:
It is a direct reading quadratic scale analog vacuum gauge.
It is a primitive method of measuring pressure known as a pressure or dead weight balance..
It consists of balances that have a vacuum chamber that is placed from above to eliminate the correction of the air pressure.
Pressure sensors are devices designed to subject materials to a pressure that deforms them in their elastic range. Such deformation is proportional to the pressure used and is considered linear.
In this way, pressure sensors transform pressure into displacement. The sensor then converts the motion into an electrical signal such as voltage or current..
The most universal pressure transducers are:
It consists of a glass tube bent in a U-shape, which is partially filled with a liquid of known density.
One end of the tube is connected to the object or space in which the pressure is to be measured, while the other end is left free.
The pressure exerted at the end where there is high pressure will cause the movement of the liquid inside the tube.
This movement will be reflected in a difference in level (or height) marked as h, which depends on the pressure and the density of the liquid in the tube..
It is a device with an elastic metal tube, which flattens and curves in a special way. When pressure is applied, the tube straightens and its free end moves.
It is this movement that moves the levers and gears, which end up moving a needle that indicates the pressure on the scale..
This instrument has an elastic component in the form of a bellows or accordion, to which the pressure to be measured is applied..
When pressure is applied, the bellows is stretched and it is this movement that displaces the measurement indicator needle..
This instrument is a variant of the bellows pressure gauge. It is shaped like a disc with concentric circular corrugations..
In this device, pressure is exerted on an elastic diaphragm, the deformation of which is translated into the movement of the pointer indicating the measurement..
The diaphragm can also be metallic, in which case it uses the elastic characteristic of the material to be measured..
This type of pressure gauge is used to measure low differential pressures or vacuum pressures.
It is the instrument used to measure atmospheric pressure. There are several types of barometers:
It is named in honor of its inventor Evangelista Torriceli, who devised it in 1643.
It consists of an 850 mm long tube that closes at the top and remains open at the bottom to fill it with mercury. The level of this liquid metal is what indicates the pressure there is.
It is the improved version of the Torricelli tube and is used in meteorological stations to obtain very precise measurements and at different scales..
It is a type of barometer that works on gas, so it is less sensitive than mercury ones, but it is practical.
It is the type of metallic barometer used to measure altitude above sea level.
It is a cylinder with elastic walls that measures atmospheric pressure variations.
It consists of an inflatable cuff, a manometer and a stethoscope that allows indirect measurement of blood pressure, by auscultation of Korotkov sounds.
It can work with mercury or air and requires the use of a stethoscope or stethoscope.
There is a variant of this device that is electronic. It is accurate and very easy to use, which is why it has become very popular. It is a device very sensitive to noise and movements.
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