Importance

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Abstract

The differential-pressure-sensing and variable-area-occluding functions of a variable-area flowmeter, or rotameter, are performed by separate, but mechanically connected, means. A housing defines a channel for flowing fluid from an upstream to a downstream location. A differential pressure sensor moves in a direction substantially perpendicular to the flowing fluid in response to the differential fluid pressure between the upstream and downstream locations. Because its movement is perpendicular to the flowing fluid, the pressure sensor is substantially insensitive to fluid friction and changes in fluid viscosity. A flow obstructor connects to the sensor and moves therewith to variably obstruct the channel and the flow of fluid from the upstream to the downstream location. Fluid frictional forces on the movement of the flow obstructor vary with changes in fluid viscosity. However the ratio of the area of the flow obstructor to the area of the pressure sensor, which ratio substantially equals the ratio of the fluid frictional forces to the pressure force, is low, typically 1:100. Consequently the overall flowmeter is relatively insensitive to changes in fluid viscosity. It typically exhibits less than .+-.1% deviation in indicated flow rate for viscosity variations on the order of .times.20. A viscosity-insensitive flow regulator functions equivalently.

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First Claim