RKI Instruments M2 Series - Manual (Page 16)

11 M2 Transmitter Operator’s Manual
connector at the bottom of the terminal PCB is used to connect the terminal PCB to the
control PCB with a ribbon cable. A 5 position connector on the left side of the terminal
PCB is used by factory or field service personnel to program the M2. On the combustible
and CO
2
versions of the M2, a factory adjust pot just above the programming connector is
used to set the detector current.
Power/Signal Terminal Strip
The power/signal terminal strip is a three position plug-in style terminal strip located at
the top of the left terminal column. It is used to connect 24 VDC power to the M2 and to
connect the 4 - 20 mA output signal to a device.
The signal output, the S terminal, does not have to be connected for the M2 to function.
The S terminal is used if you want to connect the 4 - 20 mA output signal to another device
such as a gas monitoring controller, chart recorder, or programmable controller (PLC).
Detector Terminal Strip
The detector terminal strip is a four position plug-in style terminal strip and is the middle
terminal strip in the left terminal column. For a combustible or CO
2
M2, all four terminals
are used to connect the detector to the M2. For a toxic or oxygen M2, only two of the
terminals are used for connecting a detector: two terminals are dedicated for connecting a
toxic detector and two are dedicated for connecting an oxygen detector (only one detector
can be installed).
Figure 10: Detector Terminal Strip
NOTE: The detector is factory-wired to the M2. See “Wiring the M2 Transmitter” on
page 18 for all wiring procedures related to M2.
Modbus Terminal Strip
The Modbus terminal strip is a three position plug-in style terminal strip and is the
bottom terminal strip in the left terminal column. It allows connection of the M2 into a
Modbus network.
C NC NO
C NC NO
C NC NO
ALARM 2
ALARM 1
F
AIL
A B C
RS 485
PWR/SIG
LEL
S
R
W G B
C NC NO
C NC NO
C NC NO
ALARM 2
ALARM 1
F
AIL
A B C
A B C
RS 485
RS 485
PWR/SIG
PWR/SIG
T
O
XIC O
X
Y
T
O
XIC O
X
Y
S S
Comb/CO
2
Detector
Terminal Strip
Oxy/Toxic Detector
Terminal Strip
A B C
RS 485
PWR/SIG
LEL
S
R
W G B