ABB ACQ810 - Fieldbus Grounding; Fieldbus Shield; End Termination; Pull Up;Pull down Resistors

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Quickstart Guide
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ABB PLC and drives integration using Modbus RTU
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ModbusRTU‐6‐ PLCanddrivesintegration
Hardwarephysicalconnection
Inthefollowingchapter,physicalconnectionofthehardwarewillbeexplained.
Fieldbusgrounding
For AC500, which has opto‐isolated COM interfaces, it is recommended not to connect the ground. For AC500‐
eCo, where the COM interfaces are not opto‐isolated, it is recommended to connect the ground at one place,
typicallyinthebusmaster.Forconnectionexamples,seechapter“Installationexamples”.
Fieldbusshield
TheshieldshouldalwaysbeconnectedinaModbusRTUline.ThepurposeoftheshieldistoprotectagainstEMC
disturbancesandreflectiononthebusline.Forconnectionexamples,seechapter“Installationexamples”.
Endtermination
 Purpose:Toavoidsignalreflections.
 Resistorsize:120Ohms,¼W.
 Wheretoconnect:Oneresistorineachendofthebusline(firstandlastnode).
Pullup/pulldownresistors
 Purpose:Tokeepadefinedhighlevelonthebuswhilethereisnodataexchange.
 Resistor size: Depends on bus master (COM) voltage level. 470Ωfor AC500 (5 V output) and 270Ωfor
AC500‐eCo(3.3Voutput).
 Wheretoconnect:Activatepull‐upandthepu ll‐dow
nresistors,butonly onceoneverybus line,atthebus
master.