55
Chapter 6. Flow Measurements Using the Capture
Hood
There are two methods of making flow measurement using Capture Hood:
(1)
Capture Hood (non-backpressure compensation).
(2)
Capture Hood with backpressure compensation.
(See “
Appendix A. Back Pressure
,” for an explanation of the implications of capture hood-induced back
pressure on the measured flow.)
Supply or return flows can be measured with both methods, and return flow is indicated as a negative
number. In addition, flow measurements can be performed by taking a single reading or running average
(continuous) reading mode.
Note
Keep the Capture Hood in place during the entire measurement; otherwise, the reading will be
in error.
C A U T I O N
W
HILE USING THE
A
CCU
B
ALANCE
®
AIR BALANCING INSTRUMENT TO TEST AIR
FLOW IN DUCTS
,
YOU MAY COME INTO CONTACT WITH OR BE EXPOSED TO
DUST
,
POLLEN
,
MOLD
,
FUNGUS
,
OR OTHER AIRBORNE CONTAMINANTS
.
I
F YOU
ARE OR MAY BE SENSITIVE TO DUST
,
POLLEN
,
MOLD
,
FUNGUS
,
OR OTHER
AIRBORNE CONTAMINANTS
,
ALWAYS
USE AN APPROPRIATE MASK OR
RESPIRATOR WHILE EMPLOYING THE
A
CCU
B
ALANCE
®
AIR BALANCING
INSTRUMENT
.
Single Reading Measurements
Single reading measurements are individual flow measurements initiated by pressing either the
READ
button on the meter or the red switch on the left side of the base. Depending on the flow being measured,
a single reading will take one to eight seconds to complete (lower flows take longer).
Once the measurement is complete, the flow value will be displayed. Press
SAVE
to log to memory, or
press
READ
, or red switch, to take a new measurement.
To measure in this mode:
1.
Select
Capture Hood
or
Hood BP Comp
in the
Pressure Tool
menu.
2.
Set the
Data Logging
mode to
Manual/Single
.
3.
Set the
Time Constant
to 5 seconds
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