Honeywell EK280 Applications Manual page 154

EK280
Due to the current limit for intrinsically-safe apparatus approval, the EK280 cannot supply sufficient current to
power terminal resistors. At the data transfer rate used, terminal resistors are not required.
7.5.3.1.1 Two-wire simplex – wiring
i
This function is only available since EK280 software version 2.20.
EK280
* 1 : In accordance with the above ( Chapter 7.5.3.1), no bus terminations may be used. For the most RS-
485-2-wire connections these are available or required. There are often several nodes connected to the bus,
so that a galvanic isolation must be earmarked.
In this regard, Honeywell recommends the ADAM-45 "repeater" from Advantech for the galvanic separation
as well as the proper electrical connection to the bus:
Application Manual
T-
T+
R-
R+
Ri
GND
Uext+
Uext-
Data -
Bus Master
Data + RS485 *
+
Power supply
- RS-485 (5...8 V DC)
+
Power supply
- EK280 (8 V DC)
Data -
additional bus
Data + subscribers
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