13
13
Figure 4: Location of measuring points when
traversing a round duct using the log-Tchebycheff
method
Number of
measuring points
per diameter
Position relative to inner wall
6
0.32, 0.135, 0.321, 0.679, 0.865,
0.968
8
0.021, 0.117, 0.184, 0.345, 0.655,
0.816, 0.883, 0.981
10
0.019, 0.077, 0.153, 0.217, 0.361,
0.639, 0.783, 0.847, 0.923, 0.981
The duct in Figure 5 has a horizontal dimension
between 30 and 36 inches, requiring six points (or
six traverse lines). The duct’s vertical dimension is
less than 30 inches, requiring five points (or five
traverse lines).
Figure 5: Location of measuring points for
traversing a rectangular duct using the log-
Tchebycheff method
Number of points
or traverse lines
per side
Position relative to inner wall
5
0.074, 0.288, 0.500, 0.712, 0.926
8
0.061, 0.235, 0.437, 0.563, 0.765,
0.939
10
0.053, 0.203, 0.366, 0.500, 0.634,
0.797, 0.947
Notice of Disclaimer
TSI Incorporated has made a good faith effort to
provide reliable information regarding the use of
the AXD 550 to conduct a duct traverse. However,
we cannot guarantee conformance to any
particular method of specification, or that this
material is free from error. Traverse methods
outside of the USA will be slightly different. TSI
recommends purchasing a copy of the duct
traverse specification you require from an
approved regulatory or professional organization.
For further information, refer to the 1993
ASHRAE
Fundamentals Handbook
Section 13, or to
ASHRAE Standard 111 (1988).