fluid measuring devices

7/23/2019 Fluid Measuring Devices

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Measuring

Instrumentsuse in Fluid

Mechanics



Manometer

Is an instrument that uses a column of liquid to

measure pressure, although the term is currently often used

to mean any pressure measuring instrument.

Types of Manometer1. Simple Manometer - is a tube, open at the top, which is

attached to the top of a vessel containing liquid at a

pressure higher than atmospheric! to be measured

". Micro manometer - # micro-manometer is a device that$s used to

measure very small di%erences in pressure in a gas or liquid

&. 'i%erential manometer -#n instrument in which the di%erence in pressure between two sources isdetermine from the vertical distance between thesurfaces of a liquid in tw

o legs of an erect or inverted (-shaped tube when each of the legs is conn

ected to one of thesources.

). Inverted di%erential manometer -It is used for measuring the

di%erence of low pressure, where accuracy is the prime consideration

https://en.wikipedia.org/wiki/Measuring_instrument

https://en.wikipedia.org/wiki/Measuring_instrument



*ther Measuring 'evices

McLeod Gauge A McLeod gauge isolates a sample of gas

and compresses it in a modied mercury manometer until the

pressure is a few millimeters of mercury. The technique is slow

and unsuited to continual monitoring, but is capable of goodaccuracy. nli!e other manometer gauges, the McLeod gauge

reading is dependent on the composition of the gas since the

interpretation relies on the sample compressing as an ideal

gas. "ue to the compression process, the McLeod gauge

completely ignores partial pressures from non-ideal #apors

that condense, such as pump oils, mercury, and e#en water if

compressed enough.

#neroid

#re based on a metallic pressure-sensing element that +ees

elastically under the e%ect of a pressure di%erence across the element.

#neroid means without +uid, and the term originally distinguished these

gauges from the hydrostatic gauges described above. owever, aneroid gauges

can be used to measure the pressure of a liquid as well as a gas, and they are

not the only type of gauge that can operate without +uid. For this reason, they

https://en.wikipedia.org/wiki/McLeod_gauge

https://en.wikipedia.org/wiki/Ideal_gas


https://en.wikipedia.org/wiki/McLeod_gauge





are often called mechanical gauges in modern language. #neroid gauges are not

dependent on the type of gas being measured, unli/e thermal and ioni0ation

gauges, and are less li/ely to contaminate the system than hydrostatic gauges.

ourdon 2auge

3he ourdon pressure gauge uses the principle

that a +attened tube tends to straighten or regain its circular form in

cross-section when pressuri0ed. #lthough this change in cross-

section may be hardly noticeable, and thus involving moderate

stresses within the elastic range of easily wor/able materials,

the strain of the material of the tube is magni4ed by forming the

tube into a 5 shape or even a heli, such that the entire tube tends

to straighten out or uncoil, elastically, as it is pressuri0ed.

*ri4ce 6late7

#n orice plate is a device used for measuring

the volumetric +ow rate. It uses the same principle as a

8enturi no00le, namely ernoulli9s principle which states

that there is a relationship between the pressure of the+uid and the velocity of the +uid. :hen the velocity

increases, the pressure decreases and vice versa.

https://en.wikipedia.org/wiki/Deformation_(mechanics)

https://en.wikipedia.org/wiki/Deformation_(mechanics)



*ri4ce 6late7

#n orice plate is a device used for measuring the

volumetric +ow rate. It uses the same principle as a 8enturi

no00le, namely ernoulli9s principle which states that thereis a relationship between the pressure of the +uid and the

velocity of the +uid. :hen the velocity increases, the

pressure decreases and vice versa.

;otameter <

is a device that measures the +ow rate of +uid

in a closed tube.

https://en.wikipedia.org/wiki/Flow_rate

https://en.wikipedia.org/wiki/Flow_rate

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