MGS-250 Manual
28 6490-9000
Revision
4
IMPORTANT:
Connect the RS-485 cable shield to pin 9
(board ground).
NOTE:
Selection of the Modbus Address and Baud Rate is
completed through the gas detector setup menu, described
later. No jumpers or hardware switch settings are required to
configure the Modbus communications network. This is done
electronically from the front panel display.
NOTE:
For Modbus communications with the MGS-250, t
he
default communications parameters are as follows.
x
Baud rate = 9,600
x
Parity = no parity
x
Stop bits = 1
Confirm that all devices on the Modbus communications
network (including a Building Management System) are
configured similarly.
If the MGS-250 is at the end of the RS-485 network, then be sure to set
the RS-485 terminator on the printed circuit board (PCB) to IN. This
applies a terminating resistor to the end of the wires per the
requirements of the RS-485 protocol. The terminator should be set to
OUT for all other installation conditions.
IMPORTANT:
Be sure to enable the termination resistor on
the device at each end of the network
(see
Figure 13). This
includes the Building Management System (if used).
NOTE:
Care should be exercised when changing the
terminator switch. Before powering the gas detector, use a
fine pointed device or paper clip to slide the switch position.
Do not apply force to the switch or push on the switch with
any device. The switch changes position up and down along
the access slot direction.
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