Question

What forces do we neglect when we do force balance in a deadweight tester?

Answer 1

A dead weight tester apparatus uses known traceable weights to apply pressure to a fluid for checking the accuracy of readings from a pressure gauge. A dead weight tester (DWT) is a calibration standard method that uses a piston cylinder on which a load is placed to make an equilibrium with an applied pressure underneath the piston. Deadweight testers are so called primary standards[citation needed]which means that the pressure measured by a deadweight tester is defined through other quantities: length, mass and time. Typically deadweight testers are used in calibration laboratories to calibrate pressure transfer standards like electronic pressure measuring devices.

The formula on which the design of a DWT is based basically is expressed as follows :
p=F / A[Pa]
where :
p:reference pressure[Pa]F:force applied on piston[N]A:effective area PCU[m2]
To be able to do accurate measurements, this formula has to be refined.

Absolute pressure with vacuum referenceEdit

p=
m.gl.
æ
è
1-
ra

rm
ö
ø
+P.d.t

A(20,0).(1+(ap+ac).(t-20)).(1+pnom.lp)
-(rN2-ra).gl.h+pvac

Gauge pressureEdit

pe=
m.gl.
æ
è
1-
ra

rm
ö
ø
+P.d.t

A(20,0).(1+(ap+ac).(t-20)).(1+pnom.lp)
-(rN2-ra).gl.h

NomenclatureEdit

pabsolute pressure at reference level[Pa]pegauge pressure at reference level[Pa]mtotal true mass load[kg]gllocal acceleration due to gravity[N/kg]raambient air density[kg/m3]rmaverage density mass load[kg/m3]P.d.tsurface tension effect[N]rN2density of pressure medium[kg/m3]hreference level offset DWT .. DUT[m]pvacvacuum residual pressure[Pa]A20,0PCU effective area at p=0 and 20oC[m2]aplinear thermal expansion coefficient piston[oC-1]aclinear thermal expansion coefficient cylinder[oC-1]ttemperature of PCU[oC]lpelastic deformation coefficient PCU[Pa-1]pnomnominal line pressure[Pa]pegauge pressure applied to PCU[Pa]pabsolute pressure applied to PCU


Plz mark as brainliest