General Description; Theory Of Operation: Capture Hoods And Thermo-Anemometry Sensing - TSI Alnor LoFlo Balometer El Manual Del Propietario

®
The Alnor LoFlo Balometer
compact instrument that measures very low air flow
rates in HVAC systems. It measures from 10 to 500
3
cfm (17 to 850 m /h, 4.7 to 236 l/s). The LoFlo
®
Balometer Capture Hood displays standard air volume
rate when placed at supply or return diffusers, registers,
or grilles located on the ceiling, wall, or floor.
®
Capture Hood
The LoFlo Balometer
mechanism which reduces the restriction of air flow
caused by the instrument. This unique venting system
(patent pending) allows the instrument to remain
compact while still measuring a wide range of volume
rates. The LoFlo Balometer
As air exits a diffuser, it is captured in the hood or base
and directed over a manifold. The manifold averages
the velocity pressure and directs air over the sensors.
The velocity and temperature of the air passing through
the manifold are sensed, using a constant temperature
thermo-anemometer principle. The voltage output from
the sensor is then calibrated for the entire volume rate
passing through the LoFlo Balometer
All capture hoods are susceptible to "odd" air flow
patterns. "Odd" could refer to any air flow pattern
different from the pattern where it was calibrated.
Substantial negative effects can be observed when
SECTION 1

General Description

®
Capture Hood
is a
has a vent
®
Capture Hood should be
SECTION 2
Theory of Operation: Capture Hoods
and Thermo-anemometry Sensing
®
Capture Hood.
used with the vents closed at lower volume rates, but
higher volume rates should be measured with the vents
open to minimize any resistance effects. A 2-point
measurement may be taken to compensate for the
resistance effect of the instrument at higher volume
rates.
®
The LoFlo Balometer Capture Hood is battery
powered and may be used with or without optional
hoods. It weighs just over 6 pounds with the 2' x 2'
hood, helping to reduce worker fatigue.
using a large hood on a small diffuser. For example,
using a 2' x 2' hood on a 10" x 10" diffuser. This creates
large recirculation regions on the sides of the fabric
hood and causes an "odd" air flow pattern as it passes
over the manifold. It is recommended to match the
hood closely to the size of the diffuser.
 NOTE: Throughout this manual, the units cfm, m
and l/s are used for simplicity. Note, however, that
®
the LoFlo Balometer
in standard cubic feet per minute (scfm), standard
cubic meters per hour (std. m
per second (std. l/s).
Capture Hood actually reads
3
/h), or standard liters
3
/h
1