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...1 INTRODUCTION
1.2
System Hardware – Fig. 1.2
The 4680 and 4685 transmitters are part of the EXFG Oxygen
Analyzer System which measures oxygen content and
temperature within a gas flue. The 4680/500 model is a wall-
mounted instrument and the 4685/500 model is a panel-
mounted,
DIN-sized
instrument.
transmitter can also be retransmitted to remote monitoring
equipment.
Both models have a single programmable input channel and
a single temperature input channel. Instrument operation and
programming is via four tactile membrane switches located
HAZARDOUS AREA
Flue
EXFG Probe
Process
EEx d IIB T3 (T
20°C to
to EN30014 1993 and EN30018 1995
600°C
1.1 Bar
Absolute
Maximum
(40in WG)
Test Gas
Inlet
2
Signals
from
(Zone 1, Class IIB)
Flameproof Interface Electronics Unit
EEx d IIB T6 Conforming to BS5501 Part 5: 1977
–20°C to 55°C)
amb
Reference Air Line Entry
Controlled
Heater
Supply
Control Thermocouple
Signal
Over-temperature
Trip Thermocouple
1.1 Bar
Absolute Maximum
Reference Air Unit
Fig. 1.2 System Schematic
on the front panel. Programmed functions are protected
from unauthorized alteration by a five-digit security code.
1.3
Principle of Operation– Fig. 1.2
The transmitter unit processes a 4 to 20mA (25% to
0.25% O
) signal generated at the Interface Electronics Unit
either
2
and displays the oxygen value in O
(log or linear). All ranges can be retransmitted.
In addition, the transmitter processes any alarm signals
generated from the Interface Electronics Unit – see the
EXFG Probe Guide and EXFG Interface Electronics Unit
Guide for additional system operating information.
Logic
Alarm
Signal
O
mV Signal
2
(–20 to +180mV)
Dry, Oil-free
Instrument Air
(10 bar max.)
Regulated
(003000241)
with selectable ranges
2
NON HAZARDOUS AREA
4680 Transmitter
4685 Transmitter
or
Retransmission
Output – see
Mains Supply
Section 4
or
4 to 20mA Output Signal
(25% to 0.25% O
)
2
Mains Supply
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