Serial Interface Option - Omega RD8800 User Manual

Chapter 2 Installation and Wiring

2.4 Serial Interface Option

Data can be accessed to download Configuration files or Data files using the RS232C option and a modem. The
RS485 option allows the Recorder to be installed into an existing Modbus network or it can be used to connect up
to thirty-one Recorders in series. A standard DB9 Female connector is required for the RS232 to connect to an IBM
PC compatible computer using a null modem cable and the RS232 can support cable runs up to 50 feet [16 m]. The
RS485 connection is via two wire (twisted pair) cable (a DB9 Female connector is required) and can support cable
runs up to 4000 feet [1300 m].
The Serial Interface contains an isolated switching unit for RS232 and RS485 access with a standard DB9 Female
connector. When switch 2 is in the ON position, RS485 is enabled. When switch 2 is in the OFF position, RS232
is enabled.
When more than one Recorder are connected in a series, it is necessary to apply a termination resistor on the last
Recorder. Switch 1 in the ON position applies this necessary termination resistor and should be switched to the ON
position only on the last Recorder in series.
All Serial Interface connections are made through the DB9 female connector.
The RS232 Connection to the DB9 female connector are as follows:
DB9 PIN CONNECTION
2 RxD Receive Data
3 TxD Transmit Data
4 DTR Data Terminal Ready
5 Common
7 RTS Request To Send
8 CTS Clear to Send
The RS485 (Half Duplex Mode) Connection to the DB9 female connector are as follows:
DB9 PIN CONNECTION
6 B+ Positive
9 A- Negative
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Figure 2-10 RS232/RS485 Modbus
DIRECTION
In
Out
Out
N/A
Out
In
DIRECTION
Input/Output
Input/Output
Page 2-9
SW1 SW2
On=485 Term. On=RS485
Off=RS232
1 2