Abstract: To measure flow rates, the cross-sectional shape of the flow path is changed by inserting a multiple position gate into the flow path and altering the position of the gate to maintain the head of liquid constant with a reduced flow cross section. To maintain the head at a desirable range, the depth is measured and controls the position of the gate as a feedback signal. The position of the multiple position gate is correlated with the depth to provide an indication of flow rate. For this purpose, a flow path housing is clamped to a pipe and a multiple position gate is moved by pneumatic pressure into the flow stream to change the flow cross section. The depth of the head upstream of the gate is measured and the position of the gate is measured. Flow rate is determined from these two measurements. Sampling may be performed at an increased depth caused by the gate.

Abstract: To pump liquid using a source of gas pressure, a gas-operated positive displacement pump includes an outer tubular rigid wall and an inner movable wall forming a cylindrical liquid chamber which communicates with a liquid inlet and a liquid outlet, both including check valves to permit liquid to flow into the liquid chamber through the liquid inlet and out of the liquid chamber through the liquid outlet only. Within the cylindrical liquid chamber, is a tubular gas chamber formed of an elastomeric wall capable of contacting the movable wall of the liquid chamber to compress it to cause liquid to leave and pull it back to draw liquid into the chamber, the inner air chamber being adapted to receive gas under pressure and then vented to the atmosphere alternatively. Gas between the movable wall and elastomeric wall may be squeezed into the gas chamber and held there to form a vacuum connection between the movable wall and elastomeric wall.

Abstract: An apparatus is disclosed for measuring the rate of flow of a fluid or the volume of the fluid flowing past a point. The apparatus includes a first transducer device for measuring a fluid level upstream of a weir and a second transducer device for sensing and decoding an optically encoded Gray-scale disc rotated by the first transducer device to an angular position corresponding to the level of the fluid. The disc is provided with indicia thereon proportional to flow rates and corresponding to different fluid levels. The decoded signals obtained from the disc represent the rate of flow of the fluid. These signals are then integrated to indicate the volume of the fluid flowing past a point for actuating a fluid sampler or a recording device.