General Tools CDM77535 User Manual
CDM77535
USER’S MANUAL
Digital CO
2
Environmental Meter
INTRODUCTION
Thank you for purchasing this portable CO2meter. The meter
measures CO
2
level, air temperature, dew point, wet bulb temperature
and humidity and is an ideal instrument for indoor air quality (IAQ)
diagnosis.
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Poor indoor air quality is considered unhealthy because it causes
tiredness, loss of ability to concentrate, and even illness (ex. Sick
Building Syndrome). IAQ monitoring and survey, especially on CO
2
level and air ventilation, has become widely applied in public areas
such as offices, classrooms, factories, hospitals and hotels. It is also
used in the regulations of industrial hygiene in some countries.
(Appendix)
The portable CO
2
meter uses NDIR (non-dispersive infrared) technology
to ensure reliability and long term stability. It’s useful in verifying HVAC
system performance and air ventilation control.
FEATURES:
• Triple displays of CO2level, temperature and humidity
• Stable NDIR sensor for CO
2
detection
• Statistics of weighted averages TWA (8 hours weighted average)
STEL (15 minutes weighted average)
• Backlight for working in dark area
• Audile CO
2
warning alarm
• Battery and optional adaptor power supply
• Easy manual calibration on CO
2
and humidity
• PC connect via RS232 interface
MATERIAL SUPPLIED
This package contains:
• CO
2
Meter
• 4 “AA” batteries
• Operation manual
• Hard carrying case
POWER SUPPLY
The meter is powered by either 4 “AA” batteries or a “DC” adaptor
(9V/1A output).
Install the batteries into the battery compartment on the rear and
make sure they are in correct polarity and good contact. When an
adaptor is used, it will cut off the power supply from batteries. The
adaptor can't be used as a battery charger.
When battery voltage gets low, ( ) and “Lob” will appear on the
LCD (Fig. 1). And beeper sounds. The CO
2
sensor can’t work under low
voltage, so it beeps to indicate failed CO
2
measurement (press any
key but ( ) to stop the beeps) and the readings won’t be
displayed. Please replace with fresh batteries or connect with an
adaptor.
Optional accessories:
• 33% calibration salt
• 75% calibration salt
• Adaptor (9V/100-240Vac)
• ASFT Kit, cable and software
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LCD DISPLAY
SYMBOLS
TWA . . . . . . . . . . Time weighted average (8 hours)
STEL . . . . . . . . . . Short-term exposure limit
(15 minutes weighted average)
HOLD . . . . . . . . . Readings are frozen unchanged
MIN/MAX . . . . . . Minimum/Maximum readings
(ICON) . . . . . . . . Low battery indicator
DP . . . . . . . . . . . Dew point temperature
AIR . . . . . . . . . . . Air temperature
WBT . . . . . . . . . . Wet bulb temperature
% . . . . . . . . . . . Unit of relative humidity
°E (C/F) . . . . . . . . Celsius/Fahrenheit
AVG/ftm/m/s . . . Vain icons in these models
KEYPAD
Turns on and off the meter.
Enters setup mode.
Sets as non-sleep mode with .
Exits setup page/mode.
Enters CO
2
calibration with .
Enters RH calibration with .
Freezes the current readings.
Cancels data hold function.
Activates or cancels the backlight.
Selects unit or increases value in setup.
Selects AIR, DP, WBT temps display
Selects unit or decreases value in setup.
Activates MIN, MAX, STEL, TWA function.
Saves and finishes settings.
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OPERATION
POWER ON/OFF
Press ( ) to turn the meter on and off. At power up, it emits a
short beep and performs 30 seconds count down (Fig. 2) for meter
warm up, then enters normal mode with current CO
2
, temperatures,
and humidity readings displayed (Fig. 3).
TAKING MEASUREMENT
The meter starts measurement when powered on and updates
readings every second. In the condition of operating environment
change (ex. from high to low temperature), it takes 30 sec to respond
for CO
2
sensor and 30 minutes for RH.
NOTE: Do not hold the meter close to anyyone’s face in case
exhalation affects CO
2
levels.
AIR, DP, WBT
Press ( ) to switch temperatures display. The lower left display
will cycle from air temperature, dew point temperature (Fig.4) and wet
bulb temperature (Fig. 5).
DATA HOLD
Press ( ) to freeze the readings, “HOLD” icon is displayed on the
left top of LCD (Fig.6). All current readings are kept unchanged, except
STEL and TWA. Press ( ) again to cancel the hold function.
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