When desired value is reached press the
button to save the value and
return to the main menu or press
button to return to main menu without
saving the changes
f the alarm sounds simply press any key (but power key) to silence the alarm
Changing Engineering Units
Hold down
for more than one second during normal mode to reach the main
menu
Press the
or the
to toggle between alarm setup and unit setup
When “Units” and “P3 0” are displayed on the LCD press the
button to
enter engineering unit setup
The current temperature unit will be blinking on the lower left of the display Press
the
or the
to toggle between Celsius and Fahrenheit
When desired unit is set press the
button to save and return to the main
menu or press
button to return to the main menu without saving the changes
Holding the Current Value
Press and release the
to freeze the primary temperature display “HOLD”
will appear at the top left of the screen
n order to return to normal operation press the
button again and the “HOLD”
icon disappears from the display
Max, Min, and Average Data Functions
Press the
button to cycle through the M N MAX STEL and TWA functions
To exit cycle through until none of the four mentioned functions appear on the
screen
M N and MAX readings show the minimum and maximum CO
2
readings on the
main display respectively STEL and TWA readings show the weighted average of
the CO
2
readings on the main display STEL uses all the CO
2
readings from the
past 15 minutes to calculate the average TWA uses all the readings from the past
8 hours to calculate the average The current temperature and humidity continues
to be displayed at the bottom of the LCD
Automatic Power Off (Sleep Mode)
The instrument will shut off automatically after 20 minutes of operation to conserve
battery life if no button is pressed To disable the sleep mode press “Ø set” and the
“HOLD” buttons simultaneously before power on An “n” icon will appear in the
center of the display once disabled
BATTERY REPLACEMENT
The Air Quality Handheld displays
as a visual low battery indication
When “Lob” appears on the LCD and a beeper sounds the batteries must be
replaced
To Replace the Battery
1 Make sure the unit is powered off
2 Lay face down on a clean flat surface
3 Open battery compartment by pushing in tab and lifting cover
4 Replace battery taking note of the indicated polarity
5 Replace the cover
CO
2
Calibration
The CO
2
sensor should be calibrated in fresh outdoor air that is well ventilated and
in good weather conditions Do not calibrate in areas with high CO
2
concentrations
such as crowded areas
Procedure
1 Place meter in the calibration site
2 Turn the unit on and hold down
and
simultaneously to enter CO
2
calibration mode
3 “400ppm” and “CAL” should be blinking on the display
4 Wait 10 minutes until the blinking stops and the unit returns to normal mode
To abort the calibration turn the meter off at any time
RH Calibration
The RH must be calibrated with the default calibration salt f not done properly and
with the correct salts it will cause permanent damage
33% Calibration Procedure
1 Plug sensor probe into 33% salt bottle
2 Hold down
and
under normal mode to enter 33% calibration
3 “CAL” and the calibrating value should be blinking on the LCD with current
temperature displayed but not blinking
4 Wait about 60 minutes until “CAL” and the calibrating value stop blinking
75% Calibration Procedure
1 After 33% calibration plug the sensor probe into 75% salt bottle
2 Press the
button to enter 75% calibration mode
3 “CAL” and the calibrating value should be blinking on the LCD with current
temperature displayed but not blinking
4 Wait about 60 minutes until “CAL” and the calibrating value stop blinking and the
meter returns to normal mode
Users can also calibrate either calibration point individually For the 33% calibration
point press the
once the 33% calibration is complete For the 75%
calibration point press the
or
within the first five minutes while
initializing the 33% calibration
MAINTENANCE
A periodic check of the system calibration is recommended Model AQH-20 is not
field serviceable and should be returned if repair is needed (field repair should not
be attempted and may void warranty) Be sure to include a brief description of the
problem plus any relevant application notes Contact customer service to receive a
return goods authorization number before shipping
©Copyright 2013 Dwyer nstruments nc
Printed in U S A 8/13
FR# R6-443744-00 Rev 2
M AV
N
X
M /AV
N
X
M AV
N
X
CAL
Esc
CAL
Esc
CAL
Esc
DP/WBT
MODE
DP/WBT
M /AV
N
X
CAL
Esc
MODE
HOLD
CAL
Esc
HOLD
The RH calibration should be done at 25ºC and humidity close
to the calibration salt being used (must at least be stable)
NOTICE
Model AQH-20 requires at least 5 minutes worth of values in
order to calculate either of the CO
2
averages
NOTICE
f the unit fails to power on it is likely that the batteries also need
to be replaced
NOTICE
Failing to turn the handheld off may result in malfunction of the
unit Dispose of used batteries promptly and keep away from
children
NOTICE
M AV
N
X