Connecting To A Modbus™ Network - Novatech 1635 User Manual

2.15 CONNECTING TO A MODBUS™ NETWORK
The analyser can be networked to other analysers and to a network master. The network uses the analyser RS485 port.
Up to 31 analysers can be connected to the network, and can be interrogated by the Network Master.
NOTE: Hardware Protocol Selection
For the RS485 port on the analyser to operate, the link LK3 on the 1630-1 printed circuit board (mounted on the door of
the analyser) must be set to the RS485 position. The LK3 is accessed by removing the cover from the door PCB. It is
located at the bottom of the circuit board.
NOTE: Terminating Resistor
There is a terminating 100 ohm resistor fitted to the 1630-1 PCB. Link LK2, in the bottom left-hand corner of the PCB
on the door, is used to connect the terminating resistor. Link LK2 must be removed on all analysers except the analyser
on the end of the network line. If the network line from the analysers is taken from the middle of the analyser network
string, a terminating resistor should be enabled with LK2 at each end if the network line.
The protocol of the network is –
Baud Rate
Parity
Stop Bits
RS485
Mode
For more details see Section 1.14 and Appendix 3.
22
9600
none
1
Half Duplex
RTU (binary mode)
Network Connections
August 2009
1635 Water Vapour Analyser