Emerson MICRO MOTION 2700 - Page 20

Integratethemeterwiththecontrolsystem
Tips
▪Fortypicalapplications,thedefaultvalue(0)isappropriateforFrequencyOutputMaximum
PulseWidth.Thedefaultvalueproducesafrequencysignalwitha50%dutycycle.
High-frequencycounterssuchasfrequency-to-voltageconverters,frequency-to-current
converters,andMicroMotionperipheralsusuallyrequireadutycycleofapproximately50%.
▪ElectromechanicalcountersandPLCsthathavelow-scancycleratesgenerallyuseaninput
withaxednon-zerostatedurationandavaryingzerostateduration.Mostlow-frequency
countershaveaspeciedrequirementforFrequencyOutputMaximumPulseWidth.
FrequencyOutputMaximumPulseWidth
YoucansetFrequencyOutputMaximumPulseWidthto0,ortovaluesbetween0.5milliseconds
and277.5milliseconds.Theuser-enteredvalueisadjustedautomaticallytothenearestvalid
value.
▪IfyousetFrequencyOutputMaximumPulseWidthissetto0(thedefault),theoutputwill
havea50%dutycycle,independentoftheoutputfrequency.SeeFigure2-1.
Figure2-150%Dutycycle
▪IfyousetFrequencyOutputMaximumPulseWidthtoanon-zerovalue,thedutycycleis
controlledbythecrossoverfrequency.
Thecrossoverfrequencyiscalculatedasfollows:
▪Atfrequenciesbelowthecrossoverfrequency,thedutycycleisdeterminedbythepulse
widthandthefrequency.
▪Atfrequenciesabovethecrossoverfrequency,theoutputchangestoa50%dutycycle.
♦Example:FrequencyOutputMaximumPulseWidthwithspecicPLCrequirements
ThefrequencyreceivingdeviceisaPLCwithaspeciedpulsewidthrequirementof50
milliseconds.Thecrossoverfrequencyis10Hz.
Solution:SetFrequencyOutputMaximumPulseWidthto50milliseconds.
Result:
▪Forfrequencieslowerthan10Hz,thefrequencyoutputwillhavea50–millisecondONstate,
andtheOFFstatewillbeadjustedasrequired.
▪Forfrequencieshigherthan10Hz,thefrequencyoutputwillbeasquarewavewitha50%
dutycycle.
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MicroMotionModel2700TransmitterswithIntrinsicallySafeOutputs