Rs485 Interface, Without Electrical Isolation - Honeywell Elster EK280 Applications Manual

EK280
d) Setting time window for potential data queries
In the base configuration now displayed you can define time windows, during which data can be cyclically
retrieved from the EK280 via the RS485 bus. Time windows 5 and 6 are reserved for EK280 operation with a
direct terminal interface connection, and generally only time window 5 is used. Redundant time windows can
be deactivated by setting the time window start and end to the same value.
In the top of the device window open the path "Parameter" > "Interfaces" by clicking on the relevant
plus signs, and then select
For call window 5 set the start to "00:00" and the end to "23:59" and then select the
to device" icon at the top of the enSuite window.
Press the "Transfer changes to

6.4.4 RS485 interface, without electrical isolation

If a connected RS485 interface device has a direct or capacitive ground potential connection, there is a risk
of interference coupling via ground loops, which may affect pressure or temperature measurements.
Therefore it is recommended that you use the isolated port as described in chapter 6.4.3 (page 57) if
possible.
6.4.4.1 Wiring
i
When the EK280 is connected to a RS485 bus there must be no terminal resistors connected to
the bus!
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.
6.4.4.1.1 Four-wire full duplex - wiring
EK280
Application Manual
"Call time windows".
device" icon at the top of the enSuite window.
T-
T+
R-
R+
Ri
GND
Uext+
Uext-
"Transfer changes
R-
R+
Bus Master
RS485
T-
T+
+
Power supply
- 8V (DC)
T-
T+
Further
R-
Bus participants
R+
59