User Manual

EXTECHINSTRUMENTS
4 CO240‐en‐GB_v1.412/14
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.
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hu
midityreadingswillalternateonthelowerLCDlinealongwith
theCO
2
reading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.Whi
leinMAX‐MINmode,pressandhold
theHOLDbuttonfor2secondstoreset(clear)thestoredmaximumandminimumvalues.
Selecting
o
C/
o
F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CO
2
presentas  possible. 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CO
2

levelreferencevalueduringthecalibration.Afterthecalibrationhascompleted,themeter will
returntoitsnormalmodeoperation.