18 • Chapter 3: Measuring Mode
GasWatch 3 for CO and O
2
10. If
A.ZERO
is set to
ON
(factory setting is
OFF
, see pg.85), the instrument prompts you to
do an auto zero. An auto zero operation sets the reading to 0 ppm.
WARNING:
Make sure that the instrument is in a known fresh air environment (an
environment free of combustible or toxic gases and of normal oxygen
content, 20.9%) before performing an auto zero operation. If you perform
an auto zero operation in an area with gases present, the adjustment will
not be accurate.
You must press and release the POWER/MODE button to perform an auto zero function.
If you do not press any key, after 15 seconds, the instrument enters Measuring Mode
without performing an auto zero.
11. The GasWatch 3 is now monitoring for gas in Measuring Mode. The Measuring Mode
Screen displays the current gas readings. The CO reading displays on the top line and the
O
2
reading displays on the middle line.
Performing a Demand Zero
Perform a demand zero before using the GasWatch 3. This sets the CO reading to 0 ppm and
the O
2
reading to 20.9%.
1. Find a fresh-air environment. This is an environment free of toxic or combustible gases
and of normal oxygen content (20.9%).
2. Turn on the unit as described above in “Turning On the GasWatch 3”.
3. Press and hold AIR. The buzzer pulses and the LCD prompts you to continue holding AIR
(if
KEY.TONE
is set to
ON
in User Mode).
4. Continue to hold AIR until the LCD prompts you to release it. The GasWatch 3 sets the
fresh air reading. Start up is complete and the unit is now ready for monitoring.
Turning Off the GasWatch 3
1. Press and hold POWER/MODE.
2. OFF appears on the display and the buzzer pulses for about five seconds (if
KEY.TONE
is set to
ON
in User Mode).
3. Release the button when OFF disappears from the display.
A.ZERO
YES .MODE
NO .AIR
10:42
20.9
%
0
ppm
