| 摘要 |
A piston flow meter for measuring the flow of a gaseous fluid, such as ambient air, through the flow meter by timing the displacement of a piston in a hollow precision bore flowtube over a fixed distance. The piston is reciprocated from opposite ends of the flowtube by a poppet valve which controls the direction of movement of the piston in the flowtube. Ambient air is drawn into the flow tube from the atmosphere by an external pump connected to an inlet at one end of the flowtube. The flow meter includes a damping assembly for damping pulsations in gas flow through said flowtube with the damping assembly preferably located adjacent the pump inlet to the external pump. The damping assembly comprises damping means which includes a porous member and at least one elastic diaphragm contiguous thereto with the porous member having a multiplicity of voids and a plurality of open channels extending through the porous member to the elastic diaphragm.
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