AEMC DTR 8510 - Select Filter

22 Digital Transformer Ratiometer DTR
®
Model 8510
4.3.6 Select Filter
1. FromthetoplevelofCongure Instrument,pressthe▼or▲keyuntil
Select Filterappearsonthedisplay,thenpressENTER.
Figure 4-17
2. Select Fast, Normal or Slowusing▼or▲andpressENTER.The
displaywillreturntoCongure 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:
ThedigitizationofsignalisdonewithSigma-Delta(Σ -Δ)modulator.The
outputisahighfrequencybitstreamwhichisfedtoadigitallter.The
lteringofsignalisperformedwithsophisticatedsinc(Sinx/x)lter.The
primaryfunctionofthelteristoremovethequantizationnoiseintroduced
duringthemodulationprocess.
Thelterlimitsthebandoftheallowedfrequencytosignicantlylowerthan
one-halfofthefrequencyofthemodulatoritself.Thisreducesthe1-bit
outputofacomparatorinaband-limited,verylownoiseoutput.Thecut-off
frequencyandthedecimateddatarateareappropriatelyprogrammedin
theinternalregisteredandtheoutputisarithmeticallyaveragedtoprovide
anaccuratenalanswer.
Highdecimationresultsinlowernoisebutataslowerthroughputrate.The
calculationofarithmeticmeanisaquickprocessathighclockspeedsof
themicroprocessors.
TheDTR
®
8510improvesthequalityofmeasurementsinthefollowing
ways:
(1) Lownoiseelectronics
(2) Shieldedelectronicsandcables.
(3) Differentialmeasurementstoreducecommon-modeeffects.
(4) Ratiometriccalculationstoreducedynamicerrors.
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