CMA ML66m User guide

Brand: CMA

Model: ML66m

Type: User guide

SALINITYSENSORML66M

USER’SGUIDE



CENTRE FOR MICROCOMPUTER APPLICATIONS

http://www.cma-science.nl

2|ML66mSalinitySensorUser’sGuide

Shortdescription

TheSalinitysensorML66mmeasures thesalinityofasolutioninthe rangefrom 0to

50ppt.TheSalinitysensorconsistsofaSalinityelectrodeandanamplifier.

Salinityisthemeasureofallthesaltsdissolvedinwater.Salinityisoftenexpressedas

parts per thousand (ppt), which is

 approximately equal to grams of salt per liter of

solution. The average ocean salinity is 35 ppt

and the averageriver water salinity is

0.5pptorless.



The Salinity 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SalinitysensorML66misadigitalsensorthatconvertsthemeasuredsalinityvalue

toadigitalvaluevia16‐bitanalog‐to‐digitalconversion.Themaximalsamplingrateof

thesensoris10Hz.

Howthesensorworks

The sensor determines salinity based on electrical conductivity. This Salinity probe

measures how much electrical current flows through the water. Water that has

dissolvedsaltinitwillconductelectricitybetterthanwaterwithnodissolvedsalt.The

more salt thatis dissolvedin thewater, the betterthe waterwill

conductelectricity.

Salinityisthencalculatedfromthemeasuredconductivityvalue.

The sensor has a built in compensation for changes in conductivity due to

temperature.

Calibration

The Salinity sensor is supplied with a factory  calibration and gives values in ppt. The

Coach 6 program allows shifting the pre‐defined calibration or creating a new two‐

point calibration if needed. The user calibration is  stored in non‐volatile user sensor

memory.Formoreaccuratemeasurementssensorcanbe

calibrated.

 Zerocalibrationpoint

Keepthesalinityprobeoutofanysolutione.g.,inair.Callthisvalue0ppt.

 Standardsolutioncalibrationpoint

Placethesalinityprobeintoastandardsolutione.g.,35pptandwaitforthevalue

tostabilize.Enterthevalueofthestandard

solution35ppt.



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



35gramsofsaltper1literoceanwater

ML66mSalinitySensorUser’sGuide| 3

Toprepareasolutionwithsalinityvalueof35pptat25°C:

 Pour500mLofdistilledwaterintoacontainer.

 Add33.03gsodiumchloride(NaCl)and stirthemixtureuntilallsalthasdissolved.

 Addenoughdistilledwatertomake1Lofsolution(1000mL).



Takingmeasurements

This Salinity 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.

Totakemeasurements:

 SoakthetipoftheSalinityelectrodein

distilledwaterforabout10minutes.Ifthis

isnotpossible,rinsethetipthoroughlywithdistilledwater.

 Wipe the outer part of the electrode body with a clean paper towel. Shake

vigorouslytoremoveanydropletsfromthecellchamber.

 PlacetheSalinityelectrodeinthesample

tobetested.Thesamplemustbeatleast

3cmdeeptoensurethecellchamberisfullysubmerged.

 Stirthesolutiongently,waitfor10secondstoallowthereadingstostabilize.

 Ifyouaretakingreadings inasolutionthathasatemperaturebelow10

Corabove

C,allowmoretimeforthereadingstostabilize.

 Cleanthoroughlyafterthemeasurementiscompletedtoavoidanycontamination

fortheelectrode’snextuse.Theprobecanthenbestoreddry.



Warning: Do not place the electrode in viscous, organic liquids, such as heavy oils,

glycerin(glycerol)orethyleneglycol.Do notplacetheprobeinacetoneornon‐polar

solvents,suchaspentaneorhexane.



UsingtheSalinitysensorwithMLsensors

It is very important to  know that the Salinity sensor will interact with other  ML

sensors, if they  are placed in the same solution and are connected to the same

interface (e.g., the same MoLab). This situation arises because the Salinity sensor

outputs a

 signal in the solution, and this signal can affect the reading of another

sensor.Thefollowingsensors cannotbeconnected tothesameinterfaceand placed

inthesamesolutions:

 Dissolvedoxygensensor,

 pHsensor,

 Conductivitysensor,and

More sensors can be connected at thesame time

to the interface but only one at a

timecanbeplacedinsidethesolutiontotakereadings.

4|ML66mSalinitySensorUser’sGuide

Suggestedexperiments

TheSalinitysensorcanbeusedinthefollowingexperiments:

 Measurementsofsalinityofwatersources.

 Measurethechangeinsalinityofsaltwaterasthewaterevaporates.

 Monitortherateofreactioninachemicalreactioninwhichdissolvedsalt‐ionsand

solution conductivity varies with time due

 to an ionic specie being consumed or

produced.

TechnicalSpecifications



Sensorkind Digital:on‐sensordigitalconversion

(16‐bitsresolution,communicationviaI2C)

Measuringrange 0..50ppt

Resolution ±0.00076ppt

Uncertainty(accuracy) Typical±2%aftercalibrationat25°C

Maximalsamplingrate 10Hz

Responsetime 98%offullscalereadingin5seconds

Temperaturerange 0°Cto80°C

Temperature

compensation



Automaticbetween5°Cand35°C

Cellconstant 10cm

‐1



Dimensions Sensorhousing:62x18x16mm

Connection 5‐pinsminijackplug



Warranty:

The Salinity sensor ML66m is warrante d 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.



Rev. 10/06/2012



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

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

CMA ML66m User guide

CMA ML66m User guide

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