SENSITRON
A Halma Company
MTEX4899
SMART S-MS MED
Manuale (IT)
P. 28/36
5.5
DETECTOR CONFIGURATION
The detector provides a 4-20 mA proportional output and a RS485 serial output.
5.6
4-20 MA OUTPUT CONNECTION
-
Use shielded cables.
-
Wires’ cross section depends on the distance between the control
panel and the detector: for a distance up to m 100 we advise a 3-core
wire with cross section area of 0.75 mm2; for a distance between m 100
and 200 we recommend a 3-core wire with cross section of 1.0 mm2;
for a distance between m 200 and 300 we recommend a 3-core wire
with cross section 1.5 mm2.
-
Should any junctions be necessary on wires, please make sure there is
no interruption on the shield.
-
Please remember that the shield is to be grounded from the control
panel side only. Also remember never to connect the shield to the
detectors.
-
Ensure the wire connections, either clutching or crimping type, are
properly carried out with terminals that do not oxidise or loosen. We
recommend having them soldered.
-
The SMART S-MS MED gas detectors can be connected to control
panels available on the market having 4-20mA input signals.
-
Please make sure the panels are certified according to the standards
EN60079-29-1:2016.
Figure 2 shows the connection of a SMART S-MS MED detector to a control
panel. Control panels accepting 4-20 mA input signals allow the connection of
only one detector per input.
5.7
RS485 SERIAL OUTPUT CONNECTION
To connect SMART S-MS MED gas detectors to RS485 bus lines, it is necessary
to use a 4-wire cable, 1 pair for the RS485 bus and 1 for the power supply. It is
also necessary that:
-
Wiring between the detectors and the control panel should be made by
using connection cable EIA RS485: 2 core wires with section 0.22 / 0.35
mm2 and shield (twisted pair). Nominal capacity between the wires
<50pF/m, nominal impedance 120 Ω. These features can be found in
BELDEN cable 9842 or similar (data transmission cable in EIA RS485).
Figure 2
Connection scheme for the 4-20 mA output
shield connected to the
earth (just at one side)
DL1
DL2
DL3
JP1
JP6
JP5
Power supply: Vcc-
Power supply: Vcc+
RS485:
A
RS485: B
4-20 mA
output
JP3
4
5
6
1
2
3
Not used
+
S