User manual

EXTECHINSTRUMENTS
4CO240‐en‐GB_v1.63/15
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humidity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.While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.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 CO
2
 level reference value during the
calibration. After the calibration has completed, the meter will return to its normal mode
operation.