||Dwyer Instruments part #
|Swing Vane Anemometer
||MATKII 0-3 Model 25
- Manometer-type gauge measures pressure differentials
across a cleanroom’s air filter to ensure correct filter
- Incorporates a curved, inclined-vertical tube for wide
pressure range and more increments at low readings
- Provides measurements above and below atmospheric as well
as of differential pressure
- Accurate to within ±3% of full scale
- Easy to install
This Swing Vane Anemometer helps you ensure the correct operation
of air filters and thus helps maintain the standards you require
for your cleanroom.
It provides an accurate reading (in inches of water column)
of pressure differentials across a filter. By comparing the
resistance pressure with manufacturer’s recommended values,
you can determine when a filter needs servicing or replacement
before air leakage or contamination occurs. This gauge also
helps you ensure that filters are properly installed; it should
indicate an initial reading in conformance with the manufacturer’s
Its construction is simple yet rugged. The one-piece, noncontaminating,
virtually indestructible molded white styrene-acrylonitrile
housing holds the indicating tube and fluid wells, shock mounted
glass level vial, zero adjust plunger, and leak-proof “O”
ring seals. The front panel features molded ABS knobs. The
aluminum scale is epoxy coated. Moderate overpressures are
accommodated by an overflow tank.
For normal stationary installation, simply mount the gauge
on any vertical surface with the two mounting screws provided.
A built-in spirit level simplifies leveling before mounting
screws are tightened. Fill the reservoir, adjust the fluid
level to zero, connect the tubing, and the gauge is ready
||0-3 inches water column
||Uses 0.826 sp. gr. (red
||10.5oz. (298 g.)
the Proper Air Filter and Swing Vane Anemometer*
|Air Filters are
incorporated into the ventilation system of a cleanroom
to remove an extremely wide variety of contaminants from
the air, including particles smaller than a micron, 0.000039" (0.001 mm).
Because variables involved in such ventilation systems
vary radically—depending on the exact cleanliness
standard, size of facility, rate of ventilation and many
other factors—filter selection must be made by a
qualified engineer in cooperation with the filter manufacturer.
||Once a filtering
system has been selected, one problem remains: how to
judge when the filter has reached its effective lifespan.
Because of the wide variation in the types and concentrations
of contaminants in the air being filtered, length of service
and visual inspections are an unreliable guideline. The
most widely used method of determining when a filter needs
to be serviced or replaced is to measure the pressure
drop across the filter by means of an air filter gauge.
|The Function of an Swing Vane Anemometer
|An Swing Vane Anemometer measures pressure drops across the
filter in order to determine whether or not the filter
is operating within its design range of effective use.
This is not the same as measuring filtering efficiency.
Filter efficiency has to do with the ability of the
filter to remove particulate matter from the air stream,
and is generally measured in precisely controlled tests
that vary according to the type of filter.
||One method is
to compare the weight of a carefully compounded dust mixture
trapped in the filter with the weight of the dust released.
Another method, originated by the NBS/NIST, compares the
opacity of the dust collected on filter paper from two
air samples of equal flow rate, one of which is filtered
air. The efficiency of the filter is thus evaluated on
the basis of the dust spots. A third method measures a
resistance of DOP (Dioctyl-phthalate) smoke, a homogeneous
aerosol of 0.3 micron size, to test a special class of
high efficiency filter.
Resistances for Air Filters
|All filter manufacturers supply technical data which indicate
the initial resistance in inches of water column for the
filter at its rated air flow, and a recommended resistance
at which point the filter should be replaced or serviced.
These values vary according to the type of filter. For
most filters used in a cleanroom environment, however,
the range between initial and replacement resistance is
typically between 0.01 and 0.1" WC.
||During air filter installation, air filter gauges hence
provide the additional function of ensuring proper installation
and proper air-flow design. The gauge should indicate
a pressure resistance in conformance with the manufacturer's
recommendations. If pressure is too low, the filter
may be handling less than the rated air volume due to
open bypasses or improper air balancing, incorrect installation
or air leaks. If pressure is too high after initial
assembly, the filter may be incorrectly installed or
the system may be handling more than the rated air volume.
*Source: Dwyer Control & Gauges