Appendix A: Theory Of Operation - vectus ALNOR Balometer Jr. Manuel Du Propriétaire

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THEORY OF OPERATION
The Balometer Jr. is an adaptation of the Alnor Balometer and Velometer
Jr. systems which allow this instrument to be used for measurement of air
volume by reading average velocity as the air moves through a cross-
section of known constant dimension.
The Balometer Jr. consists of six major subassemblies which function as
a system to provide accurate air flow measurements:
1. Air Collection System—All the air issuing from or entering a
diffuser is collected through a cloth ―hood‖ which is chosen to fit a
specific diffuser at one end, and translates this variable size to a
standard opening which is slightly larger than one foot square. The
diffuser end of this hood is foam-edged to allow for a complete seal
around the opening.
2. Instrument Base—The base, in addition to housing the range
selector, manifold, and Velometer Jr., provides the standard cross-
section through which the air is passed.
3. Manifold—This grid contains 16 calibrated holes in a 4 x 4 pattern
spaced within the standard base opening. It is actually two grids
back-to-back, with the pattern of holes in a separate network on each
side. Air can therefore enter the manifold from either side and be
discharged at the other. The amount of air which flow through the
manifold is directly proportional to the average velocity of the air
moving past the sensing holes. Therefore this velocity, which is
moving through a known cross-sectional area, is proportional to the
volume of air flow through the instrument.
4. Range Selector—By means of a single control, the range selector
provides for the measurement of air flow in either direction, and
provides calibrated orifices for three ranges, which effectively triples
the scale length of the meter. Accuracy of the measurement in either
direction is assured by providing similar flow paths regardless of
flow direction, and by separate calibration of each range in each
direction.
5. Velometer Jr.—TSI's standard small swing vane anemometer is
provided with a special scale graduated either in standard cubic feet
per minute or standard cubic meters per hour. Because of the direct
proportion cited earlier, this velocity reading instrument can be
directly calibrated in volumetric terms.
APPENDIX A: