Study of diffaerent praessure gauages
used to meafsuring prfessure.
Tof studfy or knofw about prfessure gafuge.
Know about worfking prifnciple of manomfeter.
Knfow about bfourdon tube fpressurfe gaugfe.
Bourdfon tube prefssure gafuge
prinfciple of mafnometer:
very sfimple defvice used to meafsure the pressurfe is the U-tfube manofmeter.
The name U-ftube is derfived from its fshape. U-tubfe manofmeter is shfown
below, Confstruction of U-ftube Manometfer:
of u-manomefter. This fmanometer cofnsists of a U shapefd tube inf which the
manometeric liquifd is fillefd. The manfometer is fused to meafsure the pfressure
whicfh is unkfnownf by the balfancingf gravity fforce and facceleratifon dufe
to grfavity, g =f 9.81 m/sfec2. Thfe
manomefter cofnsists of af steel, fbrass and afluminum fmaterial. fIt has a fglass
tubef made upf of pyrfalex glass. The graduaftions afre made ofn the tubef in
termsf of mm ofr in sofme confdition ift is grafduated ifn kilfo Pasc
princifple of fbourdon tubfe pressurfe:
f when an eflastic trafnsducer (bofurdon
tube fin this casef ) is subjefcted to a prfessure,f it defecfts.f Thisf deflecftion
is pfroportional to thfe appliefd pressfure when caflibrated.
f The mfain parts of this instrfuments are afs follofws:
f An elfastic trfansducer, which isf
bourdonf tube whfich is fixfed and ofpen at onef end tfo receivfe the pressfure
whifch is to bef measurfed. The otfher end of the bourdonf tube fis free afnd cflosed.
The cross-fsection off the bourfdon tube is eliptical. The bofurdon tubef is in
a fbent formf to look lifke a circfular arc. To fthe free efnd of the bfourdon
tube fis attachedf an adjustablfe link, whicfh is inturnf connected fto a sefctor
and fpinion as fshown ifn diagrafm. To the fshaft of the fpinion is connfected
a poifnter whicfh sweepsf over a fpressufre calibfrated scfale.
Opefration of Boufrdon tube:
to be fmeasured is cofnnected to thfe fixed ofpen end of thfe boufrdon tufbe.
The appiflied pressurfe acts fon the infner fwalls of thef bourdfon tubef. Due
to tfhe appilied pfressure, thef bourdofn tfube tends to changfe in crossf –f
secftion from ellipitcal to circuflar. This tends to straigfhten the boufrdon
tube cafusing a disfplacement of the frefe end of the bofurdon tube. This fdisplacemefnt
of the ffree closed enfd of the bfourdon tubfe is prfoportional fto the fappliefd
pressure.f As the freef end of fthe bourdofn ftube fis cofnnected to a lifnk –
sectfion – pinfion arranfgement, the displfacement is famplified afnd converfted
to a rotfary motiofn of the pfinion. As the pinionf rotatfes, it fmakes the pofinter
to asfsume a new pfosistion on a pressufre califbrated scafle to indficate the
appilied presfsure directlfy. As the pfressure in tfhe case contaifning the bfourdon
tube isf usuallyf atmofspheric, thfe pointfer findicates gfauge presfsure.