EBTRON • 1663 Hwy. 701 S., Loris SC 29569 • Toll Free: 800.2EBTRON (232.8766) • Fax: 843.756.1838 • Internet: EBTRON.com 9
GOLD SERIES GTC116 TRANSMITTER
a measurable difference!
EBTRON
IG_GTC116_R3A
4.2 GTC116‐RS‐485NETWORKWIRINGCONNECTIONS
4.2.1 GTC116‐RS‐485NetworkCableSpecifications
TheRS‐485networkcableshallbeshieldedtwistedpairwithacharacteristicimpedanceof100to130ohms.
Distributedcapacitancebetweenconductorsshallbelessthan100pFpermeter.Distributedcapacitancebetween
conductorsandshieldshallbelessthan200pFpermeter.Themaximumrecommendedlengthofa
network
segmentis1200meterswithAWG18cable.
4.2.2 GTC116‐ConnectingtoanRS‐485Network:
ConnecttheNET+,NET‐andCOMterminalswithshieldedtwistedpaircablemeetingthespecificationsdefinedin
thepreviousparagraph(typicallyusingtwopairs;onepairfor+/‐and(atleastoneof)thewiresinotherpairfor
COMwhenusing2‐paircable).Theconnectiontothenetworkmust
bemadeina"daisychain”configuration."T"
connectionsandstubsareNOTpermitted.Theshieldshouldbeterminatedatoneendonthenetworkonly.
*CAUTION
ForISOLATEDoutput,theCOMconnectionMUSTBECONNECTEDtothenetworkcommonforproper
operation.Inaddition,whentheAnalogOutputisconcurrentlyusedwiththeRS‐485Output,theCommon
connectionforbothAnalogandRS‐485Outputsmustbeatthesamepotential.
ForNON‐ISOLATEDoutput,the
COMconnectionMUSTBECONNECTEDtothecommongroundthatisused
bytheothernetworkdevices(typicallythegroundsideofthe24VACsupply;terminalL2atthePOWER
connectorblockinFigure6).Inaddition,whentheAnalogOutputisconcurrentlyusedwiththeRS‐485
Output,theCommonconnectionforbothAnalogandRS‐485Outputsmustbeatthesamepotential.
4.2.3 GTC116‐SettingTransmitterTerminationforRS‐485Network
The GTC116 is shipped with the Termination switch set for No termination, which is the recommended setting
for devices installed on the network bus anywhere EXCEPT at the ends of the bus/segment. EBTRON
recommends the following termination strategy for devices connected at the ends of the network
bus/segment:
When the transmitter is at one end of the network, it should be terminated with “End of Line” (or 120 ohm
standard) termination, and the device at the other end should be terminated with “Fail Safe Bias”
termination. This method provides proper network termination and ensures that the bus is in a known state
during idle-line conditions (when no devices are driving the bus). EBTRON GTC116 transmitters include
three termination options for “End of Line” (standard 120 ohm) and “Fail-safe Bias” (recommended at one
end of the bus) or for “No Termination”. Termination is selected by setting TERMINATION DIP switch SW3 as
shown below.
Check the network/network segment to ensure that only one device is terminated with either method. If multiple devices
are terminated as described above, network segment operation will be adversely affected.
4.3 GTC116‐TransmitterSetupforRS‐485NetworkOperation
For RS-485 operation, network connections are made on the GTC116 Combination board as shown in Figure
6, and set up is as follows. Network protocol, MS/TP address, device instance number and baud rate options
are all selected with- in the NETWORK section of SETUP menu shown in Appendix A.
NOTE:
Prior to power up, network configuration and termination switches must be set as shown in Figure 6.
Wiring to the RS-485 network is accomplished after setting the GTC116 network configuration switches.
4.3.1 GTC116‐RS‐485NetworkOptionsandCommunications
MenuSettings
The transmitter is shipped from the factory with the protocol set for BACnet MS/TP Master, address 2, MS/TP
Device ID 2, Baud rate of 76,800 and no termination. Initial RS-485 communications settings are
accomplished within the GTC116 NETWORK sub menu shown in Appendix A. Termination is set up by the
TERM DIP switch SW3 located on the Combination card shown in Figure 6.
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