AUTOMATIC PRESSURE/FLOW DEVICE

摘要

A device for the determination of the gas permeability of a material such as paper includes a holding means 1 for holding a sample across a gas flow passage of predetermined cross section and a pump 2 for drawing air through the passageway via one or more constant flow devices C1 - C6 arranged in parallel. Each constant flow device has a closable control valve V1 - V6 respectively. A transducer measures the pressure drop across the sample and a transducer the flow. A by-pass by-passes selectively three of the control valves of the constant flow devices. The by-pass has valves B1 - B3 arranged in parallel and operable to close the by-pass to gas flow therethrough to the respective constant flow devices C1 - C6. The by-pass also includes an atmospheric bleed means 11 and a valve B4 closable to stop the flow of air into the by-pass means.