Honeywell XNX - A�1 HART Interface

XNX Universal Transmitter
Appendix A - HART
®
Protocol
168
A.1 HART
®
Interface
TheXNXUniversalTransmitterisregisteredwiththe
HARTCommunicationFoundation.
Note: Onlyqualifiedservicepersonelshouldperformtheproceduresinthissection.
EveryXNX
®
gassensorcancommunicateusingtheHARTprotocol
(denedbytheHARTCommunicationFoundationathttp://www�
hartcomm�org)�HARTisuniqueamongeldbusesinthatthedigital
signalissuperimposedonatraditional4-20mAcurrentloop�This
providesthereliabilityofanalogsignalingwiththeadvanced
diagnosticcapabilityofadigitaldevice�
HARTdevicesareusuallyconnectedaspoint-to-pointnetworks�The
analogoutputoftheXNXtransmittercanalsobedisabledtofacilitate
constructionofmultidrop,all-digitalHARTnetworks�
Control System
or Other Host Application
Multiplexer
Barrier
Handheld Terminal
Field Device
Note: Instrument power is provided by an interface
or external power source that is not shown.
Figure 233. HART Point-to-point Mode
IfHARTisnotneeded,theunitcanbeusedasa4-20mAtransmitter�
Sincethetransmitterisaslave,theinternalmodemwillremainsilent
ifnomastersignalispresent�AdditionallytheHARTsignalisattoo
highafrequency(1200Hz)tointerferewithanalogcontrolequipment�
AnothernovelfeatureofHARTnetworksisthattwomasterscan
bepresent�Theprimarymasterisusuallyadistributedcontrol
system(DCS),programmablelogiccontroller(PLC),orapersonal
computer(PC)�Thesecondarymastercanbeahandheldterminal�
TheXNXtransmitterhasbeentestedwiththehandheldEmersoneld
communicator�
Input/Output (I/O) System
Handheld Terminal
Field Devices
Control System or
Other Host Application
Note: Instrument power is provided by an interface
or external power source that is not shown.
Figure 234. HART Multi-point Mode
TheXNXdevicedescriptor(DD)leprovidesHARTuserswithdata
onthecapabilitiesandfeaturesoftheXNXUniversalTransmitter�
SelectHARTenableddevicesareabletointerfacewithXNX
transmitterswhenconnectedviaHARTcommunication�Acopyof
theleisincludedontheDocumentationCD�ThisDDlecanbe
installedonHART-enabledEmersoneldcommunicatorsusingthe
EmersonEasyUpgradeUtility�TheDDleslocatedontheresource
CDarecompatiblewiththesoftwareintegraltothetransmitter�Older
transmittersusingearlierversionsofsoftwarerequirepreviousversions
oftheDDles�ContactyourlocalHoneywellrepresentativewithany
questionsregardingsoftwarecompatibility�
Duringmanufacturing,Honeywellconguresthe8-digitHARTtagto
theXNXserialnumber�Thiscanbeusedtoconrmcorrectwiring
fromthetransmittertothecontrolsystem�Ifdesired,theHARTtag
canbemodied�ThexedXNXserialnumbercanalsobereadover
HART�
Forconvenience,thetransmitterpresentstheHARTsignalontwo
interfaces�The1200HzACsignaliscapacitivelycoupledtothemain
20mAanalogoutput�Thismaybemonitoredatthecontrolsystem