CMA ML48m User guide

HUMIDITYSENSORML48M

USER’SGUIDE

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CENTRE FOR MICROCOMPUTER APPLICATIONS

http://www.cma-science.nl

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2|ML48mHumiditySensorUser’sGuide

Shortdescription

The Humidity sensor ML48m measures relative humidity in a range of 0 to 100% RH

andtemperatureintherange‐20to50°C(or‐4..122°F).Thesensorshouldnotbe

usedintemperatureabove70°C.

Two sensing elements (humidity and temperature) are placed inside the sensor box.

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The slots in the end cap of the sensor allow air circulation. The sensor working will

vary considerably with the amount of air circulation i.e. it will respond more quickly

withanincreaseinmovementofair.

The Humidity 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 aninterface is  notsuppliedwiththesensor(sensorcablesare

suppliedwithinterfaces).

Practicalinformation

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Note:

 Donotusethesensorintemperaturehigherthan70°Candinaconcentrated

(streamof)hotair.Donotusethesensorincondensingenvironments.

 Donotexposethesensortochemicalvaporsandothercontaminants.

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 The reading time of the sensor depends on the

amount of airflow in the surroundings of the

sensor.

The typical response time is 257 seconds in static

airand27secondsinmovingair(at25°C).Insome

cases, you may want to improve airflow (by

movingthesensor

orusingafan)tospeedupthe

responseofthesensor.

Sensorspecifications

TheHumidity sensorML48m is a digital sensorthat converts  the measuredhumidity

value to a digital value via 8‐bit analog‐to‐digital  conversion, and the measured

temperature value to a digital value via 12‐bit analog‐to‐digital conversion. The

resolutionofthesensoristypical0.4%RH

forhumiditymeasurementsand0.0625°C

fortemperaturemeasurements.Themaximalsamplingrateofthehumiditysensoris

20Hz,themaximalsamplingrateforthetemperaturesensoris4Hz.

ML48mHumiditySensorUser’sGuide |3

Collectingdata

This Humidity 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.

Calibration

The Humidity sensor is supplied with a factory calibration for humidity in % RH, and

for temperature in °C and °F. The Coach 6 program  allows shifting the pre‐defined

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

memory.

Suggestedexperiments

The Humidity sensor can be used to measure relative humidity of  air as part of a

weatherstation,orto:

 Study transpiration rates of plants by monitoring relative  humidity in sealed jars

containingplants.

 Optimizeconditionsinagreenhouseorterrarium.

 Determinegooddaysforstaticelectricdemonstrations.

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 Weatherstudies.

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4|ML48mHumiditySensorUser’sGuide

TechnicalSpecifications

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Sensorkind Digital(on‐sensordigitalconversion)

8‐bitsresolution forHumidity,

12‐bitsresolutionforTemperature,

communicationviaI2C

Measuringrange Humidity:0..100%,non‐condensing

Temperature:‐20..50°Cor‐4..122°F

Temperaturerangestored:‐40..125°C(‐40..257°F)

Resolution Humidity:0.4%RH

Temperature:0.0625°C

Accuracy Humidity:Typical±2%

Temperature:Typical±0.25°C

Maximumtemperature 70°Cwithoutpermanentdamageandnotina

concentrated(streamof)hotairorcondensing

environments

Respondtime

90%changeofhumidity reading:257sinstill(slowly

moving)airand27sinvigorouslymovingairat25°C

90%changeoftemperature:182sinstillairat25°C

Currentconsumption

Typical3.9mAat25°C

Maximalsamplingrate

Humidity:20Hz

Temperature:4Hz

Sensordimensions

Housing:37 x 18 x 16 mm (W xDxH)

Connection 5‐pinsminijackplug

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Warranty:

The Humidity sensor ML48m 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.

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

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

Rev. 17/11/2011

CMA ML48m User guide

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