McMillan’s patented* microturbine wheel technology utilizes the Pelton turbine wheel concept. This design allows for use of a minature microturbine wheel about 0.8 inches (20 mm) in diameter. The wheel is supported on a very small sapphire shaft, held in position by two sapphire bearings. Due to the low mass of both the wheel and the shaft, the microturbine wheel virtually floats in the liquid. This flotation effect causes the turbine wheel to be suspended in the middle of the bearings and thus eliminates shaft and bearing wear. Therefore, no particles are generated.
The rotational speed of the turbine wheel increases proportionally to the volumetric flow rate. The microturbine wheel features 8 small windows, evenly spaced around the center of the wheel. As the wheel rotates, a light beam is projected through a PTFE window and onto the wheel. A light detector on the other side of the wheel detects each window and translates those signals 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.
* US Patents 4,467,660; 5,542,302; 5,728,949. Other patents pending.