Why dead weight tester called dead weight tester?

In dead weight tester, we put the weight on the weight stand of dead weight tester putting weight is reference weight which is to be calibrate

and further we applied pressure by moving piston ,when applied pressure and reference weight(Pressure)is equal at this condition reference weight will be zero(Dead). therefore it is called dead weigh tester.

Dead weight tester

A deadweight tester (DWT) is a calibration standard which uses a piston cylinder on which a load is placed to make an equilibrium with an applied pressure underneath the piston.

The formula to design 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]