Pg7000 Differential Mode for Defining Low and Negative Differential Pressure at Various Static Pressures

Document(s): 

Pg7000 Differential Mode for Defining Low and Negative Differential Pressure at Various Static Pressures (449.27 KB)

Conventional piston gauges have limitations in the lowest pressure that can be defined, in defining negative differential pressures (i.e. differential pressures that are under the static pressure) and in defining pressures at a static pressure other than atmosphere or vacuum.

Traditionally, the minimum pressure that can be defined by a piston gauge is the pressure that results when the minimum mass load (the piston alone) is loaded on the piston-cylinder effective area. The pressure can be referenced to atmosphere (gauge pressure) or vacuum (absolute pressure) by enclosing the mass load under a bell jar. This low point tends to be poorly defined due to poor mass load distribution and low rotational momentum; it is often not low enough and cannot be defined reliably at static pressures other than atmosphere or vacuum.