CMA Current Sensor User guide

Brand: CMA

Model: Current Sensor

Type: User guide

CMA Current Sensor

The CMA Current Sensor is an I2C digital sensor that can measure currents in AC and DC circuits up to 12.5 mA. It has a very low resistance, so it introduces as little resistance as possible to the circuit. The sensor is protected and currents up to 25 mA will not damage it, but it should never be used for higher currents.

The Current Sensor can be used in a variety of experiments, such as:

Measuring the current passing through a resistor
Measuring the current passing through a LED
Exploring the relationship between current and voltage in electrical circuits

The Current Sensor comes with a factory calibration in ampere (A). The calibration can be shifted or a new two-points linear calibration can be created using the Coach 6 software. The user calibration is stored in non-volatile user sensor memory.

CMA Current Sensor

The Current Sensor can be used in a variety of experiments, such as:

Measuring the current passing through a resistor
Measuring the current passing through a LED
Exploring the relationship between current and voltage in electrical circuits

CURRENTSENSORML23F

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UIDE



CENTRE FOR MICROCOMPUTER APPLICATIONS

http://www.cma-science.nl

2|ML23fCurrentSensorUser’sGuide

Shortdescription

TheCurrentsensorML23fisageneral‐purposesensortomeasurecurrentsinACand

DC circuits in the range between‐12.5 and +12.5 mA. The sensor is equipped with

two 4‐mm banana plugs and two additional alligator clips are delivered with the

sensor.

The Current sensor should be placed

 in series with the circuit component through

whichthecurrentismeasured. Currentsineitherdirectioncanbemeasured.

TheCurrentsensorhasaverylowresistancesothatitintroducesaslittleresistance

aspossibletothecircuit.Thesensorisprotectedandcurrentsupto25mAwill 

not

damagethesensorbutitnevershouldbeusedforhighercurrents.

The Current 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).

Sensorspecifications

Forsamplingratesup1kHz(1000samplespersecond)theCurrentsensorworksasa

digitalsensorandconvertsthemeasuredcurrenttoadigitalvaluevia14‐bitanalog‐

to‐digitalconversion.Forsamplingratesabove1kHzthesensorworksasananalog

sensor. An analog signal generated

 by the sensor (on its ADC pin) is read by the

connectedinterfaceandisconvertedtoadigitalvaluebythe12‐bitADconverteron

the interface. The maximum  sampling rate of the sensor is 100 kHz (samples per

second).

Practicalinformation



CAUTION:

 NEVERconnectaCurrentsensordirectlyacrossabatteryorpowersupply,

withoutaresistancecomponenttolimitthecurrentwithintherangeofthe

sensor.Failuretolimitthecurrentwillcausepermanentdamagetothesensor.

 NEVERusehighvoltagesorhouseholdAC.

 TheCurrentsensorshouldbeplacedinserieswiththecircuitcomponentthrough

whichthecurrentisto bemeasured.

 Makesureyouobservethecorrectpolarityi.e.connecttheblackleadfromthe

CurrentSensortothenegativeterminalofthecells,otherwisethesensorwillgive

readings

withthewrongsign.

ML23fCurrentSensorUser’sGuide| 3

 Currentsineitherdirectioncanbemeasured.

Collectingdata

This Current 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 Current sensor is s upplied with factory calibration in ampere (A). The Coach 6 

program allows shifting the pre‐define d calibration or creating a new two‐points

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

memory.

Suggestedexperiments

ThisCurrentsensorcanbeusedinvariousexperimentssuchas:

 Characteristicsofalightbulbandadiode.

 MeasurementsofinternalresonanceandEMF.

 Measurementsinseriesandparallelelectricalcircuits.

 Together with a Voltage sensor it can be used to explore the relationship

betweenthe

currentandthevoltageinelectricalcircuits.



Figure2.ConnectingtheCurrentsensor

inserieswitharesistortomeasurethe

currentpassingthroughit.

Figure2. MeasuringthecurrentpassingthroughaLED.

4|ML23fCurrentSensorUser’sGuide

TechnicalSpecifications



Sensorkind Upto1000Hz‐digital

(on‐sensoranalogtodigitalconversion)

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

Above1000Hz‐analog

(on‐interfaceanalogtodigitalconversion)

Measuringrange Differential‐12.5..+12.5mA

Resolution 14‐bit,±0.002mA

Accuracy Typical±0.5%andMaximal±1.0%atfullrange

Max.overcurrentprotection ±30mA

Max.voltageinputand

Max.overvoltageprotection

±0.5V(12.5mA)

±1.0V(25mA)

Resistancebetweeninputs 40.2Ω/0.1W

Maximalsamplingrate 100kHz

Zerooffset Zero‐voltageoffsetdrift:

typical±0.008mAat25°C

Sensordimensions Housing:42x18x16mm

Electriccords:length35cm;diameter3mm

Connection 5‐pinsminijackplug



Warranty:

The Current sensor ML23f 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productistobeusedforeducationalpurposeso nly.Itisnotappropriate 

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

Rev. 15/05/2013

CMA Current Sensor User guide

Brand: CMA

Model: Current Sensor

Type: User guide

CMA Current Sensor

The Current Sensor can be used in a variety of experiments, such as:

Measuring the current passing through a resistor
Measuring the current passing through a LED
Exploring the relationship between current and voltage in electrical circuits

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CMA Current Sensor User guide

CMA Current Sensor User guide

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