GFM mass flow meter
GFM low cost aluminum or stainless steel thermal mass flow meters
Design Features
- ± 1% FS accuracy is standard
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rigid metallic construction
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available flow ranges starting from 0 to 10 sccm up to 0 to 1000 slpm
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maximum pressure of 1000 psig (70 bars)
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leak integrity 1 x 10-9 sccs of helium
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NIST traceable certification
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built-in tiltable LCD readout (some models)
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0-5 Vdc and 4-20 mA signals
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circuit protection
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can be used as a portable device
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engineering units or 0 to 100% displays
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totalizer option
A low cost solution to thermal mass flow metering for gases is presented
by Aalborg in introducing the model GFM mass flow meter line.
The
GFM design combines the convenience and accuracy of conventional mass
flow devices with low costs previously unattainable.
Each of these meters incorporate an advanced straight tube
sensor in conjunction with flow passage elements constructed of aluminum
and brass for non-corrosive gases or 316 stainless steel for corrosive
applications.
Principles of Operation
Metered
gases are divided into two laminar flow paths, one through the primary
flow conduit, and the other through a capillary sensor tube. Both flow
conduits are designed to ensure laminar flows and therefore the ratio of
their flow rates is constant.
Two precision temperature sensing
windings on the sensor tube are heated, and when flow takes place, gas
carries heat from the upstream to the downstream windings. The resultant
temperature differential is proportional to the change in resistance of
the sensor windings.
A Wheatstone bridge design is used to
monitor the temperature dependent resistance gradient on the sensor
windings which is linearly proportional to the instantaneous rate of
flow.
Output signals of 0 to 5Vdc and 4 to 20mA are generated indicating mass molecular based flow rates of the metered gas.
Flow rates are unaffected by temperature and pressure variations within stated limitations.
General Description
Compact,
self contained GFM mass flow meters are designed to read flow rates of
gases. The rugged design coupled with instrumentation grade accuracy
provides versatile and economical means of flow control.
Aluminum
or stainless steel models with readout options of either engineering
units (standard) or 0 to 100 percent displays are available.
The
mechanical layout of the design includes an LCD readout built into the
top of the transducer. This readout module is tiltable over 90 degrees
to provide optimal reading comfort. It is connected to the transducer by
a standard modular plug, and is also readily removable for remote
reading installations. Transducers without LCD readout are offered for
OEM applications.
GFM mass flow meters are available with flow
ranges from 10 sccm to 1000 sL/min N2. Gases are connected by means of
1/4” 3/8” 1/2” compression fittings and 3/4” FNPT fittings. Optional
fittings are available. These controllers may be used as benchtop units
or mounted by means of screws in the base.
Transducer power supply ports are fuse and polarity protected.
Leak Integrity
1 x 10-9 smL/sec of helium maximium to the outside environment.
