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AT-MGS-408 User Manual
3.6. Communications Connections
3.6.1 AT-MGS-408 Gas Detection Controller Network
The AT-MGS-408 Gas Detection Controller is connected to AT-MGS-410, 450, 460, 550
gas detectors using a shielded twisted pair instrument cable
(Belden 3106A or equivalent).
The maximum distance between the AT-MGS-408 and the furthest AquiTron gas
sensor when using Modbus communications is 305M. This distance is reduced when
using the AT-MGS-408 as the power source for the AquiTron gas sensors due to
voltage drops in the cable. When using the AT-MGS-408 as a power source for the
AquiTron sensors the following needs to be taken into consideration; the total power
requirements of the sensors, the wire gauge of the cable being used and the distance
to the furthest gas detector.
NOTE:
Recommended cable for Modbus and sensor power is 16-20AWG,
Belden 3106A shielded / twisted pair.
Power Requirements for AquiTron gas sensors
Model
Load
(W)
AT-MGS-410
4
AT-MGS-450
4
AT-MGS-460
4
AT-MGS-550
8
NOTE:
When using an AT-MGS-550 Gas Detector with two sensors
connected it will count as (2) channels on the controller.
The maximum distance to the furthest sensor should not exceed the following lengths
based on the total power requirements of all of the sensors to be connected to the
AT-MGS-408; i.e., (8) AT-MGS-410 sensors is a total power of 32w.
The RS-485 communication wiring between the gas monitor and AT-MGS-408 Gas
Detection Controller must be connected in the following manner:
1. Locate the Modbus/RS-485 connector in the gas detector.
(Refer to
“Figure 4-3 - AT-MGS-408 Wiring Diagram” on page 15. For additional
information, see appropriate gas monitor manual.)
2. Connect one lead of a twisted shielded pair to the “B” connection point;
note the wire color.
3. Connect the second wire to the “A” connection point; note the wire color.
4. Connect the ground to the “GND” connection point.
