The deadweight piston gauge (Bell and Howell) is used is to measure pressure in terms of fundamental units - force and area. A piston is inserted into a close fitting cylinder. Weights are placed on one end of the piston and are supported by fluid pressure applied to the other end. For absolute pressure measurements the assembly is placed inside an evacuated bell jar. Pressure measurements take into account a number of parameters affecting the instrument and its environment. they include the uncertainty of the mass of the weights and the error in the effective area measurement of the cylinder, gravity measurement, air bouyancy and temperature.
Measurement units used are Kilopascals (Kpa) or Millibars (Mb). The available range is 20 Kpa. to 300Kpa. The accuracy we feel we have is better than 0.1mb. throughout the full range.