What is a manometer?
A manometer is an instrument, which is used to measure the pressure of fluids inside closed containers, such as a tank. We can mainly find two versions to measure the pressure of gas and liquids.
What is the difference between a manometer and a barometer ?
The main difference is that the barometer is used exclusively to measure atmospheric pressure and the manometer is used only to measure the pressure in closed containers.
How does a manometer work?
This instrument is based on the same operation of the barometer since they take atmospheric pressure as a reference and measure the difference between the real or absolute pressure. There is the possibility of finding pressures above or below the pressure of the atmosphere. In the case of below or negative pressures there are instruments called vacuum gauges or also called vacuum manometers.
The most frequent units of measurement used in manometers are Kg / cm2, bar, Atm, Pa and Psi.
Parts of the manometer
Although its composition varies according to the type that is being used, we can find some parts that are essential.
- Reception: It is in charge of transforming the force generated by the pressure
- Transfer: Extends the strength of the receiving element and transmits it to the next stage
- Indication: It is facing to convert the received force towards a visual indicator
Types of manometers
Before talking about the types you have to know that we can find different types of pressure gauge classifications. such as by type of pressure, low, medium and high. We can also classify them by type of fluid to measure, gas or liquid.
Liquid pressure gauge
These instruments use the liquid as a measuring element. They are mainly made up of a glass tube, a graduated scale and the liquid that is made up of distillate and mercury. There are three different types, U-tube, Inclined tube and inkwell or well type.
This type is used to measure the pressure difference between two points in a system.
It is used to measure low pressures below 25mm.
Inkwell or well type
It is similar to the U-tube manometer, but has some important differences. At one end it has a well in which the liquid rises or falls depending on the pressure.
Elastic pressure gauge
This type uses the deformation of an elastic element as a means of measuring pressure. Within this category there are those of bourdon type, diaphragm, bellows type and inclined bell
The Bourdon manometer is possibly the most widely used pressure instrument. It is a mechanical device, which uses a spirally wound metal. When the pressure passes through this element, it loses curvature which transmits to a mechanism that moves the pressure indicator cursor.
It consists of a diaphragm in which the pressure is exerted to cause a deformation, through a mechanism it transforms this deformation into an angular movement to indicate the pressure.
It is a kind of accordion which has the possibility of contracting and expanding depending on the applied pressure. When the bellows is stretched, it moves a needle which indicates the measure.
Bourdon type bellows hood
In this device a tank is used in which a fluid and a spring are placed on top. When the pressure rises the liquid rises exerting pressure on the spring.
These gauges together use an LCD display, a pressure sensor and an electronic circuit to carry out the measurement and display it on the visual indicator.