STATUS SCIENTIFIC CONTROLS
FGD3 Infrared Gas Detector Heads
TD06/024
Issue:
7
Change Note:
1904
Page 8
3.5 Installation in a non-hazardous location
When a detector head is installed in an area where there is no potential of an
explosive gas hazard present, the cable lengths to the detector are limited solely by
the resistance of the cable. The infrared gas detector requires a minimum of 8.0V at its
Sig terminals, and 5.8V at its + terminal to allow it to operate correctly.
The maximum current loop resistance can be calculated. For systems operating at
20V, the maximum cable loop resistance (Sig) will be:
(Voltage available
– minimum voltage) / max current = max loop resistance
(20-8.0) / 0.025 = 480
.
The voltage at the + supply needs to be 1 volt greater than the required 5.8V minimum
for every 16Ω of cable resistance. At all times the voltage measured between the +
and 0V terminals at the detector head must fall within the range 5.8-7.5V.
The diagram above shows connection for FGD3 Infrared Detector Head in a non-
hazardous location. The pin numbers shown at the control unit refer to pin numbers on
the Status Scientific Controls input modules within the MCU Control Units.
Refer to the manufacturer if alternative control unit is used.
Note:
The control unit
0V is connected to
Earth.
Sig 0 +
Screen
21 Sig
22 +
23
24 0-
Summary of Contents for FGD 3 Series
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