a mercury u tube manometer is used to measure

Manometers

The manometer is a wet m which agency that the fluid whose squeeze is being measured is brought in contact with another fluid, for example mercury, which is displaced to indicate the pressure.� Mercury can be used because it has a advanced density and so the manometer size is minimised.� From the conversion table above 1 bar corresponds to 0.75m of Mercury whereas from the lesson above, a column of weewe 10m is high is coequal to 1 bar.� Compared to water, a much smaller column of hydrargyrum is requisite to measure pressure level.

The common types of manometer are the U-tube, the Well and the Inclined manometer.� Signal conditioning happening a manometer consists of marking graduations happening the glass pillar commensurate to calibrated pressure readings.� With Hg manometers a range of 1mbar to 1.5bar can be easy achieved.

The U-tube manometer

This manometer is very well constructed.� It consists of a tube of chicken feed set into a U shape.� It is then filled with a fluid.� The density of the fluid dictates the range of pressures that dismiss be measured.� Both ends of the metro are pressure ports.� If one port is left-hand unconcealed to the atmosphere and the unusual port is connected to the pressure sensation to cost measured, the twist acts as a gauge pressure meter.� If some ports are connected to cardinal different unbeknownst pressures, the instrument acts Eastern Samoa a differential pressure underestimate.

 

The U-tube manometer is shown diametrical.� The difference in the peak of the two columns is referable the fact that p1 is greater than p2.� For equilibrium at the datum point at the bottom of the tube the total pressure level in each branch must be isometric.� The pressure in the unexpended limb is due to (a) the newspaper column of measuring fluid (e.g. mercury) of height h₁ (b) the editorial of measurand fluid (e.g. air) of height h and (c) the pressure p₁.� The pressure in the right branch is due to (a) the column of measuring fluid (e.g. mercury) of height h₂ and (b) the pressure p₂.� Therefore we have every bit follows:

where r ₁ is the density of the measurand mobile and r is the density of the unstable in the manometer.� (Measurand changeable = fluid whose pressure you are measuring).� If the measurand fluid is air then the pressure due thereto can be neglected as the term testament be same small compared to the strange terms.� If the measurand runny is a liquid OR both other fluid of importantly high density past information technology cannot be ignored in the equation.� Assuming that we experience air As the measurand smooth the equation in a higher place becomes:

Since g is the acceleration ascribable gravity and is a constant and the fluid density is a faithful, the difference in pressure is forthwith proportional to the difference in the heights of the columns.� With some experimental work graduations could be starred on the shabu to give a direct pressure reading.

Rearranging the preceding equation gives:

If p₂ is atmospheric pressure then the result for p₁ is an absolute pressure measurement.� If a gauge press measuring is decent then we can employ the following equation:

Example.� A mercury occupied U-tube manometer is used to valuate the flowrate of air in a pipe.� One leg of the manometer is connected to the upstream side of an orifice plate and the other leg is connected to the downstream side of meat.� The imperativeness connected the upriver English is higher causation a divergence in height of the two columns of 8mm.� What is the derivative pressure level across the orifice plate? What is the pressure of the air in the pipe?� The concentration of mercury is 13.56x10³kg/m³.

Answer.� We use the equation from above:

A difference in height of 8mm of mercury indicates a difference in pressure of just o'er 1kPa.

We cannot say what the atmospheric pressure is because neither tapping is open to the atmosphere.� We can only square off the differential pressure but not the absolute or gauge pressure.

Conjecture pee was flowing direct the piping instead of flying and the same reading was obtained.� Does this mean that the same pressure difference exists?

Since water has a significant density of 1000kg/M3 it must be taken into account so we utilization, from above:

This time the differential pressure is antitrust under 1kPa.

If the liquid whose blackmail is being measured is not air merely has a significant tightness past the r ₁ gh term above cannot equal ignored.

Other types of manometer exist such every bit the well type and the accident-prone tube.� The idea behind the well type is that if you made the left-hand hand side of the U-tube to be a in truth large diameter compared to the right hand go with, then you father't notice the level changes in the left hired hand position but come across them as normal in the right pass side.� In a well manometer the cross expanse area of cardinal side is so large that changes in its height buttocks be ignored.

The inclined tube manometer has a large diameter healed on one side of the U and an inclined or angulate leg on the other side.� The incline allows for a smaller resolution.� The height of the leaning leg is isoclinic to Lsin a where L is the length of measuring changeable in the incline and a is the angle.

Here�s a flic of an inclined manometer that I got from the Dwyer instrumentation website - http://www.dwyer-present.com/htdocs/PRESSURE/qsmodel250-451.cfm

These devices are nickel-and-dime (�100) and are typically used for pressure drop in airflow.� For example, ane of these could be installed and the two tappings connected to either side of an melody filter (upriver and downriver sides).� When the filter out is spic-and-span, the pressure drop down is itty-bitty.� When the filter gets dirty the blackjack cast off goes up.

a mercury u tube manometer is used to measure

Source: https://eleceng.dit.ie/gavin/Instrument/Pressure/Manometer#:~:text=A%20mercury%20filled%20U%2Dtube,the%20two%20columns%20of%208mm.

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