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Abstract

A high accuracy flowmeter for testing and calibrating flowmeters and the like, and more particularly a positive displacement flowmeter which may include a cylinder (12), a piston (10) within the cylinder (12) which makes a clearance seal with the inside of the cylinder, an encoder (40) associated with the piston, and a control valve (V) for controlling the supply of a fluid flow (A1) to be measured. The flowmeter may have an arrangement for receiving differently-sized interchangeable modules for measurement of different flow rate ranges, each module having for example a compatible piston and cylinder of a predetermined size. The flowmeter includes a channel for receiving a fluid flow so as to move the piston (10) within its cylinder (12); and a device (36, 38) including the encoder (40) for detecting movement of the piston and generating electrical signals representative of the fluid flow to be measured. The movement of the piston is detected as a function of a known volume of the enclosure traversed by the piston, and a measured variable elapsed time over which the piston traverses the volume. Preferably, the flowmeter system includes a damping device (FIGS. 6A-6D) which may be mechanical, pneumatic, or fluidic. A memory device (e.g., 109) may be provided for supplying data representative of the capacity of the cell, and the fluid flow may be calculated (100) as a function of the cell capacity.

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