Micro Flow Positive Displacement Flowmeter


SMC’s ALMPD micro-flowmeter is a nutating disk positive displacement meter designed for precise measurement of ultra-low flow rates. The low-cost ALMPD offers superior value by providing a package that is capable of measuring very low flow rates with less susceptibility to wear versus other positive displacement flowmeters and the ability to work with a wider variety of hostile liquids. The ALMPD may easily be disassembled, cleaned and reassembled with reasonable care in the field. Measurement occurs as the result of the dual orbiting motion of the nutating mechanism as it rolls on the beam. Refer to figures A, B, C and D in sequence. This motion is induced by the fluid as it passes through the meter. This motion is consistent because the differential pressure forces are always great enough to ensure that the nutating mechanism travels the complete volume in each chamber. The process repeats itself 12 to 250 cycles per second, in proportion to the fluid flow through the meter. A flow signal is produced by interrupting the light from a photoemitting/detecting device. The interruptions are created by a magnet wire which tracks the magnet encapsulated in the orbiting nutating mechanism. The interruptions are then converted to an electronic square wave output, which is used to quantify the flow.