65-2660XL-XX-04 M2A-XL Transmitter
Chapter 2: Description
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11
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 OLED 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 M2A-XL 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 M2A-
XL. 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 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 M2A-XL. A factory adjust pot just above the programming
connector is used to set the detector current.
Figure 3: Terminal PCB Component Location
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 M2A-XL 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 M2A-XL 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).
Relay
Terminal
Strips
Ribbon Cable Connector
Termination Jumper
Detector Terminal Strip
Power/Signal Terminal Strip
Detector Current Adjust Pot
Programming Connector
(Factory Use)
Ground Jumper
Modbus Terminal Strip
C
NC
NO
AL
A
R
M 1
C
N
C
N
O
AL
A
R
M 2
C
N
C
N
O
FA
IL
-
S
+
A
B
C
RS
4
8
5
PW
R
/S
IG
R
W
G
B
LE
L
