Extech Instruments CO230 User manual

User Guide
Wall-Mount CO2Monitor
Model CO230
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com

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Introduction
Thank you for selecting the Model CO230 Carbon Dioxide Monitor. This
meter measures CO2 concentration, air temperature, dew point, wet bulb
temperature and relative humidity.
The audio-visual alarm and alarm relay output make this is an ideal
instrument for indoor air quality (IAQ) diagnostics. Carbon dioxide (CO2)
is a gaseous component of the earth’s atmosphere. The concentration of
CO2in natural ambient air is approximately 0.04% or 400ppm.
The NDIR (non-dispersive infrared) sensor provides stable, long term
monitoring.
This meter is shipped fully tested and calibrated and, with proper use,
will provide years of reliable service.
FEATURES
LCD simultaneously displays CO2Level, Relative Humidity, and
Temperature (air, dew point, or wet bulb)
Stable NDIR sensor for CO2 detection
Weighted averaging: TWA (8 hours) & STEL (15 minutes)
Automatic Baseline Calibration (ABC). Can be disabled for use in
areas with continuously elevated CO2levels (>400ppm)
Manual CO2calibration
Audio-visual CO2concentration warning alarm
Dew Point and Wet Bulb temperature calculations
Relay output for connecting external indicators or controllers

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Descriptions
Meter Description
1. Temperature/RH sensor
2. Main Display
3. Alarm Relay Output
4. Aux. Displays
5. 12V AC Adaptor jack
6. Keypad
7. Alarm alert lamp
8. CO2sensor
Note: Wall mount hole and relay
wiring screws are located on the back
Display Description
1. CO2concentration (ppm)
2. Relative Humidity (%)
3. Air Temperature, Dew Point or
Wet Bulb Temperature (°C / °F)
Display Icons
TWA Time weighted average (8 hours)
STEL Short-term exposure limit (15-min. weighted average)
HOLD Holds reading on display
MIN/MAX Minimum/Maximum readings
DP Dew point temperature
AIR Air temperature
WBT Wet bulb temperature
% Relative Humidity measurement unit
°E (C/F) Temperature units (Celsius/Fahrenheit)

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Keypad Description
SET Meter ON/OFF power
Setup mode
Save settings
CAL/ESC CO2calibration with ▲/DP WB
RH calibration with MXN/AVG/▼
Exit setup mode
RESET Reset the meter and clear MAX/MIN readings
Terminate Calibration
▲/DP WB Selects AIR, DP, or WBT temperature display
Selects units or increases value in calibration and setup
MXN/AVG/▼Activates MIN, MAX, STEL, TWA functions
Select mode or decrease value in calibration and setup
Operation
POWER ON/OFF
The meter is powered by a 12VDC adaptor.
Power the unit by plugging the AC adaptor into the meter and into an
AC source. The meter will switch ON with a short beep.
The LCD will perform a 30 second countdown and then displays the
current CO2concentration, air temperature, and relative humidity.

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TAKING MEASUREMENTS
The meter starts to measure when powered on and readings update
every second. If the operating environment changes (from high to
low temperature, for example) the meter requires 30 seconds for the
CO2sensor and 30 minutes for the RH sensor to stabilize.
NOTE: Do not obstruct the sensors or hold the meter close to the
mouth or any source of CO2when measuring.
AIR, DP and WBT Temperature
Use the DP/WBT button to step through AIR(air temperature), DP
(dew point temperature) and WBT (wet bulb temperature) shown on
the lower left display.
MIN, MAX, STEL, TWA MODES
In the normal mode, use the Max/AVG button to see the minimum,
maximum, and weighted average readings. Use the Max/AVG button
to step through MIN, MAX, STEL, and TWA modes in sequence and
then back to the normal mode.
In MIN and MAX modes, the meter shows the minimum and
maximum readings of CO2(main display), AIR, DP or WB
temperatures (lower left display) and Humidity (lower right display).
In STEL and TWA modes, the main display shows the weighted
average of CO2readings for the prior 15 minutes (STEL) or 8 hours
(TWA). The lower display shows the current AIR, DP/WB temperature
and humidity.

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NOTES:
1. If the meter has been powered on for less than 15 minutes, the
STEL value will be the weighted average of readings taken since
power on. The TWA mode will display a weighted average of the
readings taken during the prior 8 hours of operation.
2. The CO230 requires at least 5 minutes to calculate STEL and
TWA values. The display shows “----” during this time.
ALARM OVERVIEW
Audio-visual alarms give warnings when CO2concentration exceeds
the high limit. The meter beeps (~80dB) and flashes the LED when
the CO2level exceeds the high limit. The beeper stops when any key
is pressed or if the reading falls below the low setpoint limit.
Press and hold SET to stop the beeper. The LED lamp will continue to
flash when the beeper is manually shut off if there is still an alarm
condition. The LED will stop flashing when readings return to normal.
ALARM RELAY OUTPUT
The meter includes an internal reed relay that can be connected to
an external device (not supplied). When the CO2readings exceed the
high limit, the relay closes. When the CO2readings fall below the low
limit, the relay will open. This relay can be used to switch in an
external device. The meter can be connected to a device to control
such things as alert signs/beepers or ventilation systems for
conditioning the air quality.

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SETUP MODE (for Alarm limits and Temperature units)
In normal mode, press and hold SET to enter the setup mode. To exit
the setup mode, press CAL/ESC when P1.0, P3.0, or P4.0 is displayed.
P1.0 CO2 ALARM Upper and lower limit
When setup mode is accessed, P1.0 and “AL” are displayed.
Press SET to scroll to P1.1 to set the CO2upper limit. The current
CO2set value will be blinking.
Use the arrow ▲▼ buttons to adjust the value. Each button-press
adjusts by 100 ppm (100~9900ppm). When the desired value is set,
press SET to enter P1.2 to set the lower limit (using the same
method as for the high limit). When finished, press SET to save or
CAL/ESC to exit without saving and return to P1.0.
P3.0 TEMPERATURE UNITS (C/F)
Use the ▲/DP WB button from the P1.0 display to access P3.0.
Press SET to enter P3.1 for setting the temperature units. The
currently selected unit (°C / °F) will be blinking in the lower display.
To switch units press▲/DP WB or MXN/AVG/▼. Press SET to save
the setting or press CAL/ESC to exit without saving and return to
P3.0.

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P4.0 AUTOMATIC BASELINE CALIBRATION (ABC) ON/OFF
ABC (Automatic Baseline Calibration) is used to implement a
baseline CO2 calibration to eliminate the zero drift of the sensor. See
the next section (Calibration) for instructions on performing the
calibration. The ABC function defaults to the ON state. To disable
this feature: press ▲/DP WB while in P3.0 mode (or MXN/AVG/▼
when in P1.0 mode) to access the P4.0 settings. Press SET to enter
P4.1. The screen will flash “en” in the lower display. To disable the
ABC function press ▲/DP WB or MXN/AVG/▼until “dis” is
displayed on the LCD. Press SET to save the settings or CAL/ESC to
exit without saving and return to P4.0.
Calibration
CO2CALIBRATION
The meter is factory calibrated to a 400ppm CO2standard
concentration.
NOTE:The meter should be returned to Extech for calibration once
per year or whenever the accuracy of the meter is in question.
CAUTION: Do not calibrate the meter in an atmosphere of unknown
CO2concentration.
There are 2 options for calibration; Automatic Baseline Calibration
and Manual Calibration; see below
AUTOMATIC CO2BASELINE CALIBRATION (ABC)
Automatic Baseline Calibration (ABC) will calibrate the meter at the
minimum CO2reading detected during 7 days of continuous
monitoring. The ABC default is ON. To disable the ABC function,
please refer to the P4.0 Setup mode section above. Perform the
calibration in a well ventilated area with a CO2level near 400ppm.

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MANUAL CO2CALIBRATION
Recommendation: The manual calibration should
be performed by a qualified laboratory every 12
months.
1. Place the meter in the 400ppm calibration
chamber. Turn the meter on and hold down
the CAL/ESC and ▲/DP WB buttons simultaneously to enter CO2
calibration mode. 400ppm and “CAL” will blink on the LCD.
2. Wait approximately 5 minutes until the blinking stops. The
calibration is then complete and the meter will automatically
return to the normal mode.
3. To abort the calibration at any time, press RESET.
RH CALIBRATION
The meter is calibrated to standard 33% and 75% salt solutions.
To abort calibration press and hold the RESET button for > 1 second.
CAUTION: Do not calibrate the humidity without standard calibration
salt bottles. Otherwise, the meter will have to be returned for
specialized calibration service. Contact Extech for calibration salts or
calibration service.
33% calibration
1. Plug the sensor into the 33% salt bottle.
2. Press and hold CAL/ESC and MXN/AVG/▼to
enter the 33% calibration. “CAL” and the
calibration value (32.7%, if at 25°C) will blink on
the LCD with the current temperature shown
on the left.
3. The meter is now calibrating and will finish in
approximately 60 minutes (when “CAL” and the humidity
reading are no longer blinking).

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75% calibration
1. After the 33% calibration, plug the sensor
into the 75% salt bottle.
2. Press SET to enter the 75% calibration.
3. “CAL” and the calibration value (75.2%, if at
25°C) will blink on the LCD with the current temperature shown
on the left side of the display.
4. The meter is now calibrating and will finish in approximately 60
minutes (blinking stops). The meter will automatically return to
the normal mode.
NOTE: Single point calibrations can also be performed. To calibrate
33% only, press CAL/ESC and stop after the 33% calibration is
completed. To calibrate 75% only, press ▲/DP WB or MXN/AVG/▼
within 5 minutes of initializing the 33% calibration.