General Tools and Instruments CIH20DL - Manual (Page 9)

To power on the meter, press the button. The display will initially show the clock icon at
upper left and numbers on the primary readout counting down from 15. The numbers track
the time needed to heat the hot wire to prepare it for use. After 15 seconds, the meter will
be ready for use. It will automatically enter “normal” (air speed or airflow volume +
temperature) measurement mode and display a screen similar to Fig. 5. By default, the
primary (middle) readout shows real-time air speed in ft/min and the tertiary (lower) readout
shows real-time air temperature in degrees Fahrenheit. The secondary (upper) display also
uses °F as its default unit.
To change the default air speed or temperature unit, skip
ahead to “Using the Advanced Settings Menu,” beginning on p. 12.
MEASURING AIR SPEED AND TEMPERATURE
To measure the speed and temperature of a blower’s
or HVAC system’s output, fully extend the telescoping hot wire
probe and position the head of the probe in the airstream leaving
the system’s duct or register. Be sure the black arrow on the round
black plastic end piece points in, or opposite to, the direction of air
flow (see Fig. 6). The primary (middle) readout will show the air
speed in ft/min and the tertiary (bottom) readout will show the
temperature of the airstream in °F.
When making air speed or airflow volume measurements, it’s
important to make sure the air flows directly through the larger window in the probe
head containing the hot wire. If some of the airflow goes around the cavity, the hot wire
will not be cooled to the maximum extent, and air speed and airflow volume measurements
will consequently be low. To ensure that the hot wire is perpendicular to the airflow, slowly
twirl the probe while watching the primary (middle) readout. When the highest values are
seen, the hot wire is fully perpendicular to the flow of air.
MEASURING AIRFLOW VOLUME
To prepare to measure the amount of air exiting a duct,
grille or register, first measure its area. Then skip ahead to
“Using the Advanced Settings Menu” beginning on p. 12.
Following the instructions in Fig. 8, use the MODE SET button
and the � and � buttons to 1) place the meter in airflow
volume measurement mode and 2) enter the area of the duct,
grille or register.
Once you have measured and entered the area, fully extend the
telescoping hot wire probe and position the head of the probe
in the airstream. Make sure the hot wire window is
perpendicular to the airstream, as when measuring air speed.
The primary (middle) readout will show the airflow volume
in the default unit of CFM (cubic feet/minute) and the tertiary
(bottom) readout will show the temperature of the airstream in °F.
9
DATA
F
F
ft/min
Fig. 6. How to orient the
hot wire probe
Fig. 5. The initial display
after powering on
CIH20DL-FINAL-122111_awb 12/21/11 9:58 AM Page 9