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Digital Transformer Ratiometer DTR
®
Model 8510
4.3.6 Select Filter
1. FromthetoplevelofCongure Instrument,pressthe▼or▲keyuntil
Select Filterappearsonthedisplay,thenpressENTER.
Figure 4-17
2. Select Fast, Normal or Slowusing▼or▲andpressENTER.The
displaywillreturntoCongure Instrument > Select Filter.
NOTE: The DTR
®
8510 offers the user a choice of three digital filters for
measurement, depending upon the external electrical noise. These are
sophisticated digital filters in the design which offer maximum noise
rejection for repeatable measurements.
Digital Filters:
ThedigitizationofsignalisdonewithSigma-Delta(Σ -Δ)modulator.The
outputisahighfrequencybitstreamwhichisfedtoadigitallter.The
lteringofsignalisperformedwithsophisticatedsinc(Sinx/x)lter.The
primaryfunctionofthelteristoremovethequantizationnoiseintroduced
duringthemodulationprocess.
Thelterlimitsthebandoftheallowedfrequencytosignicantlylowerthan
one-halfofthefrequencyofthemodulatoritself.Thisreducesthe1-bit
outputofacomparatorinaband-limited,verylownoiseoutput.Thecut-off
frequencyandthedecimateddatarateareappropriatelyprogrammedin
theinternalregisteredandtheoutputisarithmeticallyaveragedtoprovide
anaccuratenalanswer.
Highdecimationresultsinlowernoisebutataslowerthroughputrate.The
calculationofarithmeticmeanisaquickprocessathighclockspeedsof
themicroprocessors.
TheDTR
®
8510improvesthequalityofmeasurementsinthefollowing
ways:
(1) Lownoiseelectronics
(2) Shieldedelectronicsandcables.
(3) Differentialmeasurementstoreducecommon-modeeffects.
(4) Ratiometriccalculationstoreducedynamicerrors.
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