Force-type flowmeter

A flowmeter capable of accurately measuring extremely low flow rates, said flowmeter comprising:

• A. a flow tube through which the fluid to be metered is conducted in the upward direction;
• B. a ferromagnetic ball disposed in said flow tube and movable therein, said tube having an upward inclination whereby said ball is subjected to the force of gravity, and in the absence of any other force, tends to fall down said tube;
• C. a position sensor operatively associated with a detection zone in said tube adjacent the low end thereof to provide a control signal when the ball lies within said zone;
• D. an electromagnet associated with said tube adjacent the high end thereof to provide, when energized, a magnetic force attracting said ball and seeking to raise it above said detection zone;
• E. a current controller coupled to said electromagnet to energize same, said controller being governed by the control signal from said position sensor and generating a magnet current to energize said electromagnet, said position sensor producing a control signal which causes said magnet current to pulse and said ball to oscillate at a rate depending on the flow rate of the fluid;
• and F. means indicating the frequency of said current to provide a reading of flow rate.