MMR SB1000 User Manual


Page|10
41 Daggett Drive, San Jose, CA 95134
Phone: +1 (650) 962 9620 Fax: +1 (650) 962-9647 Email: info@mmr-tech.com Web: www.mmr‐tech.com

GeneralOperation

However,oneshoulduseasmalltemperaturedeviationΔTinordertoobtainrepresentativedata
inthetemperaturedomain.Therefore,thevaluesofV1andV2willalsobesmall.Becauseofthis,
a direct measurement will not give high accuracy because of instrumental errors, and any
undesired
thermo‐voltageeffects fromwires,connectors,etc.Theseeffectscancreatesubstantial
offsetvoltageswhich,inadditiontothetemperaturedriftsandoffsetsoftheinputamplifiers,can
contributeamajorsourceofmeasurementerror.Thesecanbeeliminated,however,bytaking
measurementsattwodifferenttemperatureoffsets,usingtwodifferent
powersettings,andthen
usingthedifferencesignal.Weshowthisasfollows;therealvaluesofV1andV2acquire dbythe
SB1000aregivenby:
 (4).V1(P
1)=ε1 ∆T(P1)+ ∆V1and
 (5).V2(P
2)=ε2∆T(P2)+ ∆V2

WhereΔV
1andΔV2aretheinstrumentandextraneousthermaloffsetvoltagesdiscussedabove,
andP
1isthepowerapplie d totheheateratthefirstmeasurementpoint.Now,iftheheaterpower
ischangedtoanewvalueP
2,weobtainasecondpairofvaluesforV1andV2:
 (6).V1(P
2)=ε1 ∆T(P2)+ ∆V1and
 (7).V2(P
2)=ε2∆T(P2)+ ∆V2

TheoffsetvoltagesΔV1andΔV2canbeassumedtobeindependentofpowerP,becauseonlythe
temperature in the immediate neighborhood of the reference and sample junctions change, not
thosewheretheseotheroffsetvoltagesoriginate.

Subtractingequations(6)and(7)from(4)and(5),
respectively,weobtainthetruevalueofε1from
thefollowing:

 (8).
ε1=ε2{V1(P1)‐V1(P2)}/{(V2(P1)‐V2( P2)}

(8)doesnotincludeΔV1andΔV2.Theoffsetshavebeenremoved.

Certainhardwareandsoftwareprecautionshavealsobeenimple mentedtoeliminateanypossible
electricalcouplingbetweentheheaterandmeasurementcircuitsas well. 






MMR SB1000 Specifications

General

Brand	MMR
Model	SB1000
Category	Controller
Language	English