RKI Instruments M2A - Manual (Page 58)

53 M2A Transmitter Operator’s Manual
Adding an M2A to an Existing M2 Modbus Installation with Alternate Wiring
An M2A can be wired into an existing M2 Modbus system. The shape of the terminal PCB will be
different but the wiring connections are identical and the ground jumper on the M2A must still
remain installed.
Termination Jumper
The M2A includes a 2-pin termination header (see Figure 9) that is used when the M2A is used in a
Modbus system. Every M2A is supplied with a termination jumper (a jumper block) installed onto
this header. If the M2A is not used in a Modbus system, this jumper has no function. When the
M2A is installed in a Modbus system, this jumper must be installed in an M2A that is at the end of
a Modbus line. Any M2A in a Modbus system that is not at the end of a line must have the
termination jumper removed (see Figure 29 & Figure 30 below).
Figure 29: Multiple M2As in a Daisy Chain Configuration
Modbus
Master
Up to 128 M2As can be connected without a repeater RS-485 RS-485
ID = 126 ID = 127
M2A
Termination
Jumper
Not Installed
M2A
Termination
Jumper
Not Installed
ID = 128
M2A
Termination
Jumper
Installed
ID = 125 ID = 1
M2A
Termination
Jumper
Not Installed
M2A
Termination
Jumper
Not Installed