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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.

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  • The relative simplicity of the ALMPD makes it far less costly than other PD flowmeters desigined for low-flow rate measurement.
  • Reduced susceptibility to wear versus other PD technologies as a result of the following design features:o Micro-machined components with reduced size resulting in lower relative velocities amongst the moving partso Any forces acting on one side of the
  • Since the moving parts are not rigidly attached to each other or the motion detection mechanism, the ALMPD is capable of service in fluids less filtered than other devices which may be capable of measuring similar low flow rates.
  • Should the MICRO FLOWMETER become clogged with debris, it can be easily disassembled, cleaned and reassembled with reasonable care in the field.
Process Connections:¼” NPTF
Measuring Principle:Nutating Disk Positive Displacement
Materials:All wetted parts are SS#316 / PTFE
Temperature:-40~180 °F (-40~80 °C)
Operating pressure:3,000 psig (21 MPa) Standard21,000 psig (147 MPa) Optional
Accuracy:±1.0% of range
Ranges:FMTD4: <0.015~4.00 GPH (1-250 CC/min)FMTD20: <0.075~20.00 GPH (5-1250 CC/min)
Repeatability:±0.1% of range
Max Δ Pressure:FMTD4: 5 psid (34 kPa)FMTD20: 15 psid (102 kPa)
Max Viscosity:100 SSU (25 cP) Recommended
Displacement:FMTD4: ≈ 50 pulses/ccFMTD20: ≈ 10 pulses/cc
Output Signal:0-5 VDC square wave pulse
Weight:2.9 lbs (1.32 kg)
Cable Length:3 feet (1 M) standard
Conduit Connection:½” NPT
Power Supply:8~30 VDC
Approvals:CSA explosion proof, Class I, Div I grp. C & D
Power Consumption:50 mA maximum
Dimensions:2.5” Dia x 4.63 L (6.4 cm x 11.8 cm)

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