CMA ML60m User guide

GASSENSORML60M

USER’SGUIDE



CENTRE FOR MICROCOMPUTER APPLICATIONS

http://www.cma-science.nl

2|ML60mCO

GasSensorUser’sGuide

Shortdescription

The CO

2

Gas sensor ML60m is used to monitor gaseous carbon dioxide levels in the

range of 0 to 5000 ppm

. The sensor uses the Non‐Dispersive Infrared Detection

(NDIR) method and detects the net increase or decrease of light that occurs at the

wavelengthwhereabsorptionofcarbondioxidetakesplace.Thelightintensityisthen

correlated to CO

 c oncentrat ions. CO

 gas moves in and out of the sensor tube by

diffusionthroughthesixventholesinit.Thetubecontainsaninfraredsourceatone

end and an infrared detector at the other end. The detector measures infrared

radiation absorbed in a narrow band centered at a wavelength of

4.26 µm. The

greatertheconcentrationofthe absorbinggasinthesamplingtube,thelessradiation

is detected by the IR detector. When  the sensor is co llecting data, the IR source

blinkingonandoff–ittakesareadingaboutevery3seconds.

Thesensorisdeliveredwitha

250mlsamplingbottleandrubberstoppertoattachthe

sensortubetothebottle.

Donot place thesensor tubedirectlyinto anyliquid.The sensoris intended onlyfor

measuringgaseous,notaqueous,CO

concentrations.



The CO2 Gas sensor is an I2C digital sensor, which gives calibrated values of the

measured quantity. This sensor can only be connected to special interfaces that

supportI2CdigitalsensorsliketheCMAMoLabinterface.Thesensorcableneededto

connect the sensor to MoLab is not supplied with the

 sensor, it is supplied with

MoLab.

Sensorspecifications

TheCO

2

GassensorML60misadigitalsensorthatconvertsthe measuredCO

2

inppm

toadigitalvaluevia12‐bitanalog‐to‐digitalconversion.Themaximalsamplingrateof

the sensor is 1 Hz. Due to the measurement process of the sensor the optimal

samplingrateis20perminute.

Collectingdata

This CO

2

Gas sensor works only with specific interfaces. The sensor will be

automaticallydetectedwhenconnectedtosuchaninterface.Fordetailedinformation

aboutmeasurementswithsensorsconsulttheUserManualsoftheinterfaceandthe

Coach6software.





TheCO

sensormeasuresinpartspermillion(ppm).

Ingaseousmixtures,1partpermillionrefersto1partbyvolumein1millionvolumeunitsofthewhole.

Thisunitcanberecalculatedtopercentbydividingavalueinppmby10000.5000ppmisequalto0.5%.

ThelevelofC0

2

intheEarth’stropospherehasgraduallyincreasedfrom317ppmin1960tocurrent

levelsofnearly370ppm.ExhaledhumanbreathhasaC0

concentrationofabout50000ppm.

ML60mCO

GasSensorUser’sGuide |3

Calibration

The CO

2

Gas sensor is supplied with a  factory calibration for CO

 level in ppm. The

Coach 6 program allows shifting the pre‐defined calibration if needed. The  user

calibrationisstoredinnon‐volatileusersensormemory.

ThesensorcanbecalibratedatoneknownCO

levelusingthecalibrationbuttonon

thesensorbox.

- Placethe250‐mlsamplingbottlelongenoughintheairoutsidetoensurethatits

contentisreplacedwithfreshair.ThecalibrationwillbebasedontheCO



concentrationleveloffreshairofabout390ppm.Whilestilloutdoorsinsertthe

sensorwiththerubberstopperintothebottle.Youcannowtakethebottleand

thesensortothelocationwherethemeasurementsaretobedone.

- ConnecttheCO

sensortoaninterface.

- Letthesensorwarmupbycollectiondataforatleast90seconds.

- Whenthereadingsarestabilizeduseapapercliporaballpointtopressdownthe

calibrationbutton.Afterabout30seconds,thereadingshouldstabilizeatavalue

ofapproximately

390ppm(plusofmin40ppm).

- Ifthereadingissignificantlylowerorhigherthan390ppm(whilestillinfreshair),

simplypressthebuttonagaintorepeattheprocess.

Additionalinformation

 TheCO

sensorneedstowarmupfor90secondsanytimewhenpoweris

interrupted.

 Thesensorrequiresalargecurrent(120mA).WerecommendthatyouusetheAC

connectorfortheinterfacewhenusingtheCO

sensor.OnlyoneCO

sensorcanbe

usedatatime.

 ThesensorcannottakereadingsataCO

concentrationhigherthan5000ppm.

OncetheCO

concentrationreachesthislevelthecomputerwillcontinuetodisplay

areadingof5000ppm,untiltheactualleveldropsbelow5000ppmagain.

 EventhoughthesensorrespondsratherquicklytochangesinCO

concentration,

rememberthatgashastodiffusethroughtheholesinthesensortubebeforeany

changesinconcentrationwillbedetected.Sincediffusionofgasesisafairlyslow

process,thereisaresultingdelayinthereadings.

 Thesensorisdesignedtooperatebetween20°Cand30°C.

Thesensorcanbeused

outsideofthistemperaturerange;howevertherewillbealossinaccuracyof

readings,evenifthe1‐pointcalibrationatthelowerlevelorhighertemperatureis

done.Allowenoughtimeforthesensortostabilizeatthedesiredoperating

temperatures.

4|ML60mCO

GasSensorUser’sGuide

Suggestedexperiments

 MeasuringCO

levels(respiration)fromsmallanimalsandinsects.

 Monitoring CO

2

changes in a plant terrarium during photorespiration and

photosynthesisinlight/dark(combinationwiththelightsensor).

 MeasuringCO

levelsduringcellularrespirationofpeasorbeans.

 MonitoringproductionofCO

duringchemicalreactions.

 MeasuringCO

levelsinclassrooms.



TechnicalSpecifications



Sensorkind Digital12‐bitsresolution

(on‐sensordigitalconversion)

communicationviaI2C

Measuringrange 0..5000ppm

Resolution 2.44ppm

Accuracy

100ppmintherangeof0‐1000ppm

10%ofreadingintherangeof1000–5000ppm

Maximalsamplingrate

1Hz

Warm‐uptime 90seconds(maximum)

fasterwhenaircirculates

Respondtime

90%offullscalereadingin60s

Normaloperationtemperature 25°C

Operatinghumidityrange

5

–

95%(non‐condensing)

Connection 5‐pinsminijackplug

Warranty:

The CO

 Gas sensor ML60m is warranted to be free from defects in materials and

workmanshipfor a periodof12monthsfromthedateofpurchaseprovidedthatithas

been used under normal laboratory conditions. This warranty does not apply if the

sensorhasbeendamagedbyaccidentormisuse.



Note:Thispro ductistobeusedforeducationalpurposesonly.Itisnotappropriatefor

industrial,medical,research,orcommercialapplications.    

Rev. 10/06/2012

CMA ML60m User guide

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