B-1
APPENDIX B
RS-232/485 COMMANDS
RS-232/485 COMMANDS
The RS-232/485 interface enables the analyzer to be remotely controlled by a host remote
device such as, a PC, PLC, datalogger, etc. On the rear panel of the analyzer there are
two male DB9 connectors. Both connectors are identical, so either can be connected to
the remote device. The remaining connector can be used to connect a second analyzer.
Using a daisy-chain configuration, several analyzers can be connected to one remote
device.
RS-232 CONNECTION
A null modem (crossed) cable is required when connecting the analyzer to an IBM
Compatible PC. However, a straight cable (one to one) may be required when connecting the
analyzer to other host remote devices. As a general rule, when the connector of the host
remote device is female, a straight cable is required and when the connector is male, a null
modem cable is required.
DATA FORMAT
1200, 2400, 4800, or 9600 BAUD
8 data bits
1 stop bit
no parity
All responses are terminated with a carriage return (hex 0D)
RS-485 CONNECTION
The instrument uses a four wire RS-485 configuration with automatic flow control (SD).
The pin configuration for DB9 connector on the rear of the instrument follows:
Pin# (DB9) Function
4 + receive
8 - receive
2 + transmit
7 - transmit
5 ground
INSTRUMENT IDENTIFICATION NUMBER
Each command sent to the analyzer must begin with the instrument's identification
number plus 128. For example, if the instrument ID is set to 25, then decimal 153
precedes each command. The analyzer ignores any command that does no begin with its
instrument identification number.
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