5
65-2619RK-CH4-4 M2 Transmitter Operator’s Manual
Internal Description
This section describes the internal components of the M2. The internal components of the
M2 include the terminal PCB which provides for all the wiring connections to the M2 and
the control PCB which displays the gas reading and has the control buttons.
Figure 2: M2 Internal Components
Terminal PCB
The terminal PCB is encapsulated in epoxy for protection against moisture and physical
damage. It is mounted into the rear of the junction box with three standoffs and rests on a
thin layer of foam. A banana jack is screwed into each of the standoffs and used for
mounting the control PCB. The terminal PCB converts the electrical output from the
detector to a signal which can be displayed by the LCD display, a 4 - 20 mA signal (that is
proportional to the detection range), and an RS-485 Modbus output signal. The 4 - 20 mA
signal may be used by a recording device, gas monitor controller, or programmable
controller. The Modbus output may be used to connect the M2 to a Modbus network. The
terminal PCB also controls three relays, one fail and two gas alarm relays.
Two columns of plug-in style terminal strips are used to make all wiring connections to
the M2. The column on the left consists of the power/signal, detector, and Modbus
terminal strips. The column on the right consists of the relay terminal strips. A 20 position
connector at the bottom of the terminal PCB is used to connect the terminal PCB to the
Alarm 1 LED
Fail LED
TX LED
RX LED
Alarm 2 LED
UP/YES
ENTER
LCD Display
ENTER
DOWN/NO
Push Button
Control Switches
C
N
C
N
O
AL
AR
M
1
LE
L
R
W
G
B
R
W
G
B
FA
IL
C
N
C
N
O
PW
R
/SI
G
-
S
+
-
S
+
Detector Terminal Strip
Power/Signal
Terminal Strip
Programming
Connector
(Factory Use)
Detector
Current Pot
(Factory
Adjust)
UP/YES
DOWN/NO
Termination
Jumper
View With Cover Removed
Modbus
Terminal Strip
View With Cover and
Control PCB Removed
Display
Ribbon Cable
Connector
3/4" NPT Conduit Opening
for Wire Entry
LE
L
P
W
R
/S
IG
RKI INSTRUMENTS
M2 TRANSMITTER
A
B
C
R
S
485
A
B
C
RS
4
8
5
AL
A
R
M
2
C
N
C
N
O
Relay
Terminal
Strips
Junction Box
Magnetic
Switches
Terminal PCB
Control PCB
3/4" NPT Conduit
Opening for
Detector J-Box
Wiring
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