Appendix B Serial Communications - Michell Instruments Liquidew I.S. User Manual

Liquidew I.S. User's Manual
Appendix B Serial Communications
To communicate with the monitor:
• Connect to the serial port using the wiring defi ned below.
• Set the address of the monitor using the front panel.
• Set the desired communication protocol (ASCII or Modbus RTU) via the
front panel or over the serial interface.
• Determine the register number of the parameter to be read.
• Send the correct command to the monitor and decode the response.
RS485 Wiring
The Liquidew I.S. monitor uses a 2-wire RS485 connection.
Pin numbers in the manual refer to standard pins on the DB9 D-Sub connector on the rear panel of
the MCU:
Male DB9 Pinout (Liquidew I.S. Monitor on MCU Panel)
It will be necessary to match up the A/B (Differential data pair) and GND (0 V) pins with the wiring
of your own third party adaptor.
E.g. For the K3-ADE RS232->RS485 adaptor use the following wiring:
Pin Name
GND
This wiring is the generally accepted standard for most 2-wire RS485 equipment.
Michell Instruments
Pin Name
A
B
GND
1
Liquidew DB9 Pin
A
B
Liquidew DB9 Pin
3
2
5
B A GND
2 3 4 5
6 7 8 9
K3-ADE DB9 Pin
3
2
5
APPENDIX B
8
3
5
51