Calibration of carbon dioxide sensors General
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1. a al airCarbon Sensors Simple remote environmental monitoring wma Calibration of carbon dioxide sensors Important Before you calibrate your carbon dioxide sensor be sure that you have correctly set the altitude pressure variable in your sensor See the user manual for more information For best accuracy we recommend a calibration once every four to six weeks General calibration steps either calibration method Always wait to calibrate the sensor until it has been continuously powered for a minimum of 20 minutes This allows the sensor to warm up To calibrate press the Menu button until the Set recalibration CO2 level screen is displayed Use the and buttons to set the value to the CO level This is dependent upon the method you choose below Now press the Menu button once to view the Hold and to recal CO2 screen Hold both buttons The sensor will adjust its parameters If the calibration is successful you will see a Calibration Successful screen Your sensor is now calibrated and ready for use If the calibration is not successful try it again If you continue to have problems contact airCarbon Method 1 Using outside air to calibrate For most applications outside air is an accurate and effective calibration source Outdoor carbon dioxide is generally a well mixed atmospheric gas That is it typically remains ata relatively constant slowly changing level Currently this level is near 390 pp2. erences 1 Mauna Loa CO observatory http www esrl noaa gov gmd ccgg trends 2 Grimmond C S B et al Local scale fluxes of carbon dioxide in urban environments methodological challenges and results from Chicago Environmental Pollution 116 2002 Available http www kcl ac uk ip suegrimmond publishedpapers Chicago_CQO2 202002 EPVOL116PS24358254 pdf Last accessed March 2011 2010 airCarbon Sensors LLC www aircarbon com
3. m 1 Although carbon dioxide is generally well mixed in the atmosphere in locations near carbon dioxide sources such as running vehicles factories humans etc carbon dioxide can vary For rural areas and small towns this variability it rarely more than 20 ppm above the well mixed level of 390 ppm For metropolitan areas the daily maximum can be 80 ppm or more above this level Also because of weather and climate effects carbon dioxide is generally better mixed in mid afternoon than in the morning For these reasons as a general rule calibrate your sensor in the mid afternoon For more information review the research in 2 To calibrate using outside air take your sensor to an outside area away from running vehicles people animals and other carbon dioxide sources Let the sensor carbon dioxide value settle for about 20 minutes Since human breathing creates a significant amount of carbon dioxide for best results leave the sensor during this time Then follow the steps above for calibrating the sensor using the outside air carbon dioxide value of 390 ppm Method 2 Using calibration gas If you purchases a sensor with an external port you have the capability using calibration gas 2010 airCarbon Sensors LLC www aircarbon com airCarbon Sensors sees Simple remote environmental monitoring a Calibration gas can be obtained from several sources eg JJS Technical Services For best results purchase a calibratio
4. n gas with a concentration that is similar to the concentrations that you plan to measure For example if you are monitoring a greenhouse and your levels are typically around 1200 ppm select a 1000 or 1500 ppm calibration gas You will also need a gas flow regulator valve for the calibration gas Poor calibration will occur with excess pressure so choose a gas flow regulator that flows 0 5 liters per minute lpm or less To calibrate with calibration gas first set the recalibration CO2 level according to your calibration gas using the directions above Then press Menu until you return to the data display screen Install the valve on the calibration gas cylinder Connect the valve to the sensor using vinyl tubing available at most hardware stores Turn on the calibration gas valve You should seen the data display begin changing within 30 seconds Wait for the CO data value to stabilize Now press the Menu button until you see the Hold and buttons to recal CO2 screen Hold the buttons until you see the recalibration start Once you see the screen Calibration Success shut off the gas Your sensor is now calibrated If it still does not calibrate successfully contact airCarbon support Be sure to shut off your calibration gas when finished Calibration with a 1000 ppm calibration gas 2010 airCarbon Sensors LLC www aircarbon com ER airCarbon Sensors z Simple remote environmental monitoring wma Ref
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