Model MCX-32
Model MCX-32 Instruction Manual
Rev. 2.3
Page 15 of 49
4.6 Serial Output Gas Sensors (RS-485)
Serial output gas sensors can be interfaced directly to the MCX-32 controller without the need for I/O
modules.
This is accomplished by connecting the sensors in series to the controller’s Port 1 or Port 2
Modbus
™
interface. Each serial sensor must have a unique Modbus
™
address and be connected to the correct
port for the controller to communicate properly.
Connect the five wires of a Modbus
™
capable sensor (Detcon Model 600 and Model 700 Series, typically) to
the DIN rail mounted terminal block labeled “RS-485 PORT1” or “RS-485 PORT2” and corresponding power
terminal block labeled “VDC Out”. Each sensor connected to the Modbus
™
must have a unique Modbus
™
Address, typically starting at 01h (hex). The channel number the sensor is associated with is dependent on the
Modbus
™
address. (Modbus
™
addresses are hexadecimal. Channels numbers are decimal. A conversion
chart can be found in Section 11.1.)
Sensors addressed between 01h and 20h (channels 1-32) must be
connected to Port 1. Sensors addressed between 21h and 40h (channels 33-64) must be connected to Port 2.
Port 1 or Port 2
Output Terminal Blocks
R
S
-4
8
5
V
D
C
O
u
t
A
B
+
Figure 11
Modbus
™
(Serial) Gas Sensor Connections
NOTE:
Serial sensors addressed between 01h and 20h (channels 1-32) must be connected to
Port 1. Serial sensors addressed between 21h and 40h (channels 33-64) must be connected to
Port 2.
If the Controller has only serial sensors connected, a System Auto Configuration can be performed. This can
be accomplished by entering the ‘Menu’, and selecting ‘AUTO CONFIGURE SYSTEM’. This will initiate
the auto configure function and the controller will then poll each possible Modbus
™
address starting at 01h to
see if a serial sensor is attached. If a Modbus
™
capable sensor is attached to the address being polled, the
controller will gather that sensor’s information and populate that sensor’s Channel Details screen with the
information obtained. This information includes: sensor type, sensor range, sensor life, gas type, and current
reading. If the controller does not see or recognize a sensor at an address, the controller will mark that address
as ‘OFF”, and move on to the next address. When the auto configuration has completed going through all 64
addresses, it will proceed to find any RL-4’s and finally any AO-4’s.
More information on ‘AUTO
CONFIGURE SYSTEM’ can be viewed in section 6.3.1.
After completing the auto configuration, the Channel Details screen for each sensor should be checked for
accuracy. AUTO CONFIGURE SYSTEM does not complete the controller’s configuration. Some variables
are set to default, (such as Alarm set points,) and may need to be adjusted for proper operation. The channel
Description is left blank and the RL4 Bank Select for each sensor will default to all three banks assigned.
4.7 Auxiliary Relays
The Interface PCA contains terminals for connection to the Auxiliary Relays (Fault and No-Comm). Wiring
to these relays should be brought directly to the Interface PCA. The terminal blocks on the Interface PCA are
