Sentek RT6, Hardware Manual

Page: 37 / 90

CHAPTER 4: SYSTEM INSTALLATION
Page 33
jumper must be on only the first logger and the last
logger on the RS485 cable. If it is not present
communications may be unstable on a long cable run
(see Appendix I - RS485 connections).
Jumper JP2 "RS232/RS485" is used to select either
RS232 or RS485 external communications.
To
enable external RS232 connection the
“RS232/RS485” jumper JP1 should be in the
“RS232” position as marked.
Front
panel/remote
switch
Also, the switch on the Front Panel should be set to
“Remote” position for communication through the
external RS232 connection or to “Front Panel” for
local communication through front panel RS232
connector.
RS485 cabling
Multiple RT6 logging facilities can be connected
together (multi-dropped RS485) on a twisted pair
screened data cable back to a computer. Note normal
telephone cable is not suitable. Although only one
pair is required for RS485 communication it is
recommended that at least a two pair cable be
installed in the event of failure.
Cable lengths up to 1km from computer to last logger
can be used depending on cable specifications and
data rate (baud rate). If problems are experienced
with communication then lower baud rates should be
tried.
The cable must daisy chain from logger to logger
without the use of junction boxes or joins which
effect the efficiency of the cables screen. Under no
circumstances are T-joins to be used as this will effect
reliable data transmission.
All “A” wires are connected together and all “B”
wires are connected together and all screens are
connected together. See Appendix I for wiring
diagrams.