Extech Instruments CO240 User manual

USER MANUAL
Carbon Dioxide Meter
Model CO240
Additional User Manual Translations available at www.extech.com

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Introduction
Thank you for selecting the Extech Instruments Model CO240. The CO240 measures Carbon
Dioxide (CO2), Air Temperature, and Relative Humidity. It also calculates Dew Point Temperature
and Wet Bulb Temperature. The user-programmable high alarm feature alerts the user when
CO2level rises above the programmed limit and the data streaming feature allows readings to be
captured in real time by PC (USB connection). This device is shipped fully tested and calibrated
and, with proper use, will provide years of reliable service. Please visit our website
(www.extech.com) to check for the latest version of this User Guide, Product Updates, and
Customer Support.
Features
•Portable meter measures CO2, Air Temperature, and Relative humidity accurately
•Measures CO2(0~9,999ppm) using NDIR (Non-dispersive Infrared Technology)
•Dual display indicates Relative Humidity/Air Temperature and CO2
•Calculates Dew Point and Wet Bulb Temperature
•Adjustable CO2high alarm threshold with audible beeper
•Tripod mount
•USB cable for PC data streaming
•Battery or AC Adaptor Powered

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Meter Description
1. Sensors
2. LCD Screen
3. HOLD / Up Arrow Button
4. MODE / Left Arrow Button
5. SET Button
6. AC Adaptor jack
7. Tripod Mount
8. POWER ( ) Button
9. (Max/Min) / Right Arrow Button
10. UNIT Button
11. Down Arrow Button
12. USB PC interface port
Battery compartment on rear of meter.
Operation
Powering the meter
Momentarily press the POWER button to power on the meter. Hold the POWER button for 2
seconds to turn off the meter. During measurement, if the alarm is sounding (audible beeper)
press the POWER button momentarily to turn off the beeper. Press again to activate the beeper
function. The alarm beeper is set to ON by default. The meter can be powered by 6 AAA
batteries or AC Adaptor.
Recommendation: For datalogging, power the unit using an AC/DC adaptor in order to conserve
battery power.

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Auto Power Off
The CO240 will automatically turn off after 20 minutes of inactivity. To disable the auto power
off function: With the meter OFF, press and hold the HOLD button and then press the POWER
button. The LCD will show “n”, and will then return to normal measurement mode.
Measurements
When the meter is turned on, a self-test is implemented. Due to the nature of the NDIR sensor,
it typically requires approximately ten minutes to obtain stable, accurate readings. If the USB
cable is connected to the CO240, the USB symbol will be shown on the LCD.
The temperature and relative humidity readings will alternate on the lower LCD line along with
the CO2reading on the top display line. Use the MODE button to switch to DP (Dew Point
Temperature) and WB (Wet Bulb Temperature) modes (lower display line).
Maximum and Minimum Readings Memory
Momentarily press the MAX/MIN button to review the maximum and minimum readings
captured since the meter was powered on. Pressing the button once will show the maximum
value. Pressing the button again will display the minimum value. Pressing the button a third time
will return the meter to its normal mode of operation. While in MAX-MIN mode, press and hold
the HOLD button for 2 seconds to reset (clear) the stored maximum and minimum values.
Selecting oC/oF units of measure
Press the UNIT button to select the desired temperature unit of measure.
Calibration
Press and hold the SET + UNIT buttons for 2 seconds to enter the self-calibration mode. Ensure
that there is as little CO2present as possible. It is recommended that this be done in outside air.
The LCD will display “CAL” and will perform a 60-second countdown as it performs the
calibration. A reading of “400” is displayed as a normal CO2level reference value during the
calibration. After the calibration has completed, the meter will return to its normal mode
operation.
Automatic CO2 Baseline Calibration (ABC)
The ABC algorithm continually tracks the sensor’s lowest reading over a fixed time interval and
slowly corrects for any long-term drift (as compared to the expected fresh air value of 400ppm).
The ABC period is 15 days, during which the ABC function default is always on.

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CO2Alarm Setting
Press and hold the SET button for 2 seconds to enter the high CO2alarm threshold. Press the
HOLD button to increase the value, and the Down arrow button to decrease the value. Press the
MODE button to select the digit to the left and press the MAX/MIN button to select the digit to
the right. Once the desired value is set, press the SET button for 2 seconds to save the alarm
setting. The LCD will return to its normal mode of operation. The meter alarm limit default is
1000ppm (OSHA). Momentarily press the POWER button to toggle the alarm on and off.
PC Software
This meter has the capability to connect to and communicate with a PC.
Check the software download page of the website www.extech.com/software/downloads for
the latest version of the PC software and its operating system compatibility.
Download and unzip the software. Run ExtechInstaller.exe and then refer to the instructions
provided in the HELP Utility within the software program.

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Maintenance and Troubleshooting
Battery Replacement
When the battery icon appears on the LCD, the batteries must be replaced.
In a downward motion, slide the rear battery compartment cover off of the meter housing.
Remove the old batteries and replace with new batteries (all of the same type) observing correct
polarity. This meter uses six (6) 1.5V AAA batteries. Please replace the battery compartment
cover before attempting to use the meter.
Battery Safety Reminders
oPlease dispose of batteries responsibly; observe all relevant regulations.
oNever dispose of batteries in a fire; batteries may explode or leak.
oNever mix battery types; install new batteries of the same type.
Troubleshooting / Error Message Displays
Erratic Readings Replace the batteries or use the AC/DC adaptor and check again.
ER1 Display CO2, Temperature or Humidity sensor failure or a sensor communication
error. Send for service if display persists.
ER2 Display Out-of-range condition for CO2, Temperature or Relative Humidity.
Detected reading exceeds CO2, Temperature or Humidity range
specification. This error is normal when clearing the maximum and
minimum readings in the MAX/MIN mode.
“9999” Display Reading exceeds the CO2maximum measurement range or the battery
power is weak.

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Specifications
Display
Dual multifunction LCD
CO2measure range
0 to 9,999ppm
CO2accuracy
± (75ppm + 5% of reading) 0 to 2,000ppm
Operating Temperature
32 to 122°F (0 to 50°C); 0.1° resolution
Temperature Accuracy
± 1.8°F (1.0 °C)
Operating Relative Humidity
0 to 95%RH (avoid condensation)
Relative Humidity Accuracy
± 5% of rdg at 77°F (25°C) otherwise ±7% RH
Dew Point Temperature range
-99.22 to 118°F (-72.9 to 47°C); 0.1° resolution
Wet Bulb Temperature range
12.2 to 118.8°F (-11 to 48.2°C); 0.1° resolution
Storage Temperature
-4 to 122°F (-20 to 50°C)
Storage Humidity
0 to 95%RH (avoid condensation)
Power
AAA batteries x 6 pcs or AC adaptor
Dimensions
8.3 x 2.4 x 1.6” (211 x 60 x 40 mm)
Weight
6.4 oz. (181.4g)

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Two-year Warranty
Teledyne FLIR warrants this Extech brand instrument to be free of defects in parts and
workmanship for two years from date of shipment (a six-month limited warranty applies to sensors
and cables). To view the full warranty text please visit:
http://www.extech.com/support/warranties.
Calibration and Repair Services
Teledyne FLIR offers calibration and repair services for the Extech brand products we sell. We
offer NIST traceable calibration for most of our products. Contact us for information on calibration
and repair availability, refer to the contact information below. Annual calibrations should be
performed to verify meter performance and accuracy. Product specifications are subject to change
without notice. Please visit our website for the most up-to-date product information:
www.extech.com.
Contact Customer Support
Customer Support Telephone List: https://support.flir.com/contact
Calibration, Repair, and Returns: [email protected]
Technical Support: https://support.flir.com
Copyright ©2022 Teledyne FLIR Commercial Systems, Inc.
All rights reserved including the right of reproduction in whole or in part in any form
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