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LIQUID FLOW CONTROL PRODUCTS

McMillan’s patented* liquid flow control technology utilizes the Pelton turbine wheel concept. This design allows for use of a miniature turbine wheel similar in size to a U.S. dime (16 mm diameter, 0.75 mm thick). The wheel is supported on a very small sapphire shaft, held in position by two sapphire bearings. Due to the light weight of both the wheel and the shaft, the microturbine wheel virtually floats in the liquid. This flotation effect relieves force on the shaft and bearings, virtually eliminating wear.

As flow passes through the microturbine sensor, it is directed onto the very small teeth of the wheel using a precision-machined nozzle. This nozzle is sized according to the flow range of the unit. The rotational speed of the turbine wheel increases proportionally to the volumetric flow rate.

MICROTURBINE CUTAWAY
The microturbine wheel has alternating white and black sections evenly spaced on one surface of the wheel. As the wheel rotates, an infrared beam is reflected off each white section and is directed to a phototransistor which detects each reflected beam and converts them into pulses. As the wheel spins faster, pulse rate increases. When the wheel stops (under zero flow conditions), no pulses are generated. Consequently, zero drift is not possible and zero adjustments are never required. Processing circuitry provides pulse and/or analog outputs that are linearly proportional to the flow rate.

The output from the flow sensor is analyzed and compared to the flow rate set point. The proportional-control needle valve is then automatically adjusted to achieve the required flow. The flow rate set-point is supplied by an external electrical source. The logic used by the FLO-CONTROLLER is illustrated in the diagram below.


FLOW CONTROL DIAGRAM

* US Patents 4,467,660; DE 19680105 T1; GB 2302175B; GB 2332064B; Japan 1770103; other patents pending.