Instrumentation : Dead Weight Tester

A dead weight tester apparatus (DWT) is a device used for the standard calibration of  a pressure gauge . 

The video tutorial explains the about the  construction and working of DWT apparatus. DWT method works on the principle of Pascal's law or the principle of transmission of fluid-pressure (a change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid) . 

DWT apparatus consist a piston and cylinder arrangement on which load is placed, the load of the weight is balanced by pressurising the fluid inside the apparatus using the pressure pump present in the DWT device. 

Mathematical formulae used in DWT method

1. Δ P= ρg(Δh)
   where :
   Δ P : change in hydro-static pressure
   ρ : fluid density
   g : acceleration due to gravity
   Δh : height of fluid above the point of measurement
2. p = F / A       [Pa]
   where:
   p : reference pressure   [Pa]
   F : force applied on piston   [N]
   A :effective area PCU    [m2]