CMA ML51m User guide

MAGNETICFIELDSENSORML51M

USER’SGUIDE



CENTRE FOR MICROCOMPUTER APPLICATIONS

http://www.cma-science.nl

2|ML51mMagneticFieldSensorUser’sGuide

Shortdescription

TheMagneticFieldsensorML51mmeasuresmagneticfieldstrengthintherangeof

‐1000to3000Gauss(‐100.. 300mT).ThesensorusesaHall‐elementasitssensing

element.Thiselementismountedatthetipofthestainlesssteeltube.

The face of Hall element is

directed perpendicular to the direction of the stainless

steel tube and the sensor is most sensitive when the tube is positioned parallel to

magnetic field lines. The sensor is therefore very suitable for measuring magnetic

fieldinsidecoilsornearpermanentmagnets.

The Magnetic Field 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).



Note:

Thevaluesobtainedbythesensorwillbesensitivetothepositioninmagneticfield

andtheorientationofthesensortothefielddirection.Afalselowvaluecouldbe

achievedifthedirectionofmagneticfieldisnotparalleltothedirectionofthesensor

tube.



Sensorspecifications

The Magnetic Field sensor ML51m is a digital sensor that converts the measured

magnetic field strength value to a digital value via 14‐bit analog‐to‐digital

conversion. The re solution of the senor is 0.244 gauss. The maximal s a mpling

frequencyofthesensoris1000Hz.

Collectingdata

This Magnetic Field 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 Magnetic Field sensor is supplied with a factory calibration in gauss (G). The

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

pointlinearcalibrationifneeded.UsetheSet tozerooptioninCoach6toadjustthe

zero point of the sensor. The

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

memory.

ML51mMagneticFieldSensorUser’sGuide |3

Suggestedexperiments

ThisMagneticFieldsensorcanbeusedfor:

 Measurementsofthemagneticfieldneara(strong)permanentmagnet.

 Measurementsofthemagneticfieldnearacurrent‐carryingwire.

 Measurementsofthemagneticfieldnearorinsideacoilorsolenoid.

 ThevariationofthefieldinHelmholtz

coils.



Figure1.Measuringthemagneticfieldnearapermanentmagnet.

Magneticfieldstrengthmeasurement

Magneticfieldstrength(also knownasthemagneticfluxdensity)isameasureofthe

forcethemagneticfieldwillexertonanelectriccurrentoranothermagnet.

In S.I. units magnetic field strength is expressed in teslas (T). In cgs units magnetic

fieldstrengthisexpressedingauss(G).

1G=1x10

‐4

T=0.1mT



Belowaregivenmagneticfieldstrengthvaluesofexemplarymagneticsources.



Magneticfieldstrength

ingauss

Magneticfieldsource

‐9

–10

‐8

 Thehumanbrainmagneticfield

0.31‐0.58 TheEarth’smagneticfieldonitssurface

25 TheEarth'smagneticfieldinitscore

50 Atypicalrefrigeratormagnet

100 Asmallironmagnet

2000 Asmallneodymium‐iron‐boron(NIB)magnet

15,000‐30,000 Amedicalmagneticresonanceimagingelectromagnet

4|ML51mMagneticFieldSensorUser’sGuide

TechnicalSpecifications



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

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

Measuringrange ‐1000..3000gauss

Resolution Typical0.244gauss

Uncertainty

Radiometrysensitivityerror:

Typical±1.5%atfullrangeandtemperatureof25°C

Linearitysensitivityerror:Typical±3.5%

Accuracy:Typical±5.0%

Currentrequirement

Typical27mAat25°C

Maximumsampling

1000 Hz

Sensordimensions

Housing:70 x 21 x 70 mm (WxDxH)

StainlessSteelProbe:

Length:130mm

Diameter:7mm

Connection 5‐pinsminijackplug



Warranty:

TheMagneticFieldsensorML51m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only.Itisnotappropriate

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

Rev. 17/11/2011

CMA ML51m User guide

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