XITRON XT2640 - Inside the Xt2640; General Measurement Methods

XT2640OperatingManual 13July2016 Page160of187
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25 INSIDETHEXT2640
ThissectionisintendedtogiveyouaninsightintotheinternalstructureoftheXT2640.InordertousetheXT2640knowledgeofthe
internaloperationoftheXT2640isnotnecessary.InmanyplacesafulldescriptionisnotprovidedtoprotectIPrights.Thediagram
belowisasimplifiedblockdiagramofthemeasurementflowinsideaXT2640.
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25.1 GENERALMEASUREMENTMETHODS
AllmeasurementresultsobtainedwithintheXT2640arebasedondigital22or24‐bitresolutionsamplesobtainedofthevoltageand
currentsignalsprovidedtoeachoftheXT2640channels.Theanalog‐to‐digitalconversiontechniqueusedintheXT2640isa
proprietary2‐stagecompoundADCmethod.
Thesignalsthemselvesarenotmodifiedpriortosamplingotherthanfixedscalingandminimallow‐passfilteringtoreducesampling
anomaliesandtheonlymodificationsmadetothesamplesare–
 Applicationofcalibrationscalingandoffsets.
 Addingorsubtractingscaledcurrentsamplesfromthevoltagessamples,orviceversa,tocompensatefortheVorAterminal
burdenofthechannelasenabledbytheADJUSTconfigurationsetting.
 Low‐passfilteringaccordingtotheBANDWIDTHconfigurationsetting.
ThefollowingmeasurementsareallperformedbytheXT2640atalltimesasrequired,unlessotherwisestatedtheseare
continuouslyappliedusingallsamplesofthesignals–
Frequency ThefrequencyofaselectedvoltageorcurrentsignalwithineachVPAhasitsfrequencymeasuredusing
allsamplesobtainedfortheselectedsignal.Frequencyisdeterminedusingthereciprocalperiodofzero
valuecrossingsoftheband‐passfilteredselectedsignalsamples.
Highestandlowestpeaks Thehighestandlowestofallsamplesobtainedforeachsignalwithineachmeasurementperiodare
recordedasthehighestandlowestpeakmeasurementresults.
Lowesthalf‐cyclevalley Thelargestofallsamplesobtainedforeachsignalwithineachhalf‐cycleofthefundamentalperiodis
recorded,thesmallestoftheserecordedhalf‐cyclesampleswithineachmeasurementperiodisrecorded
asthesignalvalleymeasurementresults.
Othernon‐harmonicmeasurementresults.Allothernon‐harmonicmeasurementsareperformedusingallsampleswithineach
measurementperiod.AllACandAC+DCmeasurementresultsaretheRMSvalues,andallDC
measurementresultsarethemeanvaluesduringeachmeasurementperiod.
Harmonicanalysis Ananti‐aliasedsub‐setofthesamplesusedfornon‐harmonicmeasurementswithineachmeasurement
periodareusedforDFTbasedharmonicanalysis;eachsetiscollectedandanalysedbeforeanotherset
maybecollected(forEN61000‐3‐2and‐12theanalysisisperformedwithineachmeasurementperiod
sothereisneveradelaybetweenperiods).
Spectralanalysis Ananti‐aliasedsetofsamplesareusedforDFTbasedspectrumanalysis;eachsetiscollectedandthen
analysedbeforeanothersetiscollected.
Scopetriggerdetectionandcapture.Asetofsamplesareusedforscopetriggerdetectionandcapture;eachsetiscollectedandthen
analysedbeforeanothersetmaybecollected.
InallcasesthemeasurementresultsobtainedfromtheXT2640aredirectlytheresultsoftheseanalyses;forexampleneitherthe
measurementresultsnorthecalibrationscalingappliedaremodifiedforsignalfrequencycontent.
CHANNEL
CIRCUITRY
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CONTROL
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MEASUREMENTS
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MEASUREMENTS
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MEASUREMENTS
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MEASUREMENTS
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