Section I
General Information
DESCRIPTION
The R8471A Combustible Gas Controller monitors a 4
to 20 milliampere (ma) dc signal generated by a Det-
Tronics combustible gas sensor/transmitter assembly.
The single channel system operates in the range of 0
to 100% LFL (lower flammable limit). Controller
response includes actuation of solid state or optional
relay outputs for direct control of field response
devices, a full array of faceplate indicators, as well as
an optional 4 to 20 ma output for transmitting system
information to other monitoring devices.
FEATURES
• Controller accepts a 4 to 20 ma input, ensuring
compatibility with a variety of transmitters.
• Digital display, bar graph display, and high intensity
LEDs indicate important system status information.
• AutoCal feature ensures easy and accurate calibra-
tion.
• Microprocessor based controller is easily field pro-
grammable to meet the needs of a specific applica-
tion.
• Base model is furnished with solid state alarm and
fault outputs.
• Premium model is furnished with relay outputs and a
4 to 20 ma dc output.
• Current output is selectable for isolated/non-isolated
operation.
• Rack compatible with Det-Tronics R7400 series
flame controllers.
• Variety of racks available in 4U or 3U height config-
uration.
SPECIFICATIONS
CONTROLLER
OPERATING VOLTAGE—
24 vdc. Can operate in the range of 18 to 32 vdc.
MAXIMUM RIPPLE—
Ripple should not exceed 5 volts peak-to-peak. The
sum of dc plus ripple must be ≥18 vdc and ≤ 32 vdc.
POWER CONSUMPTION (controller only)—
Base model: 0.7 watt nominal, 1.3 watts maximum
(25 ma nominal, 50 ma maximum at 24 vdc.)
Premium model: 1.2 watts nominal, 3.5 watts maxi-
mum (50 ma nominal, 145 ma maximum at 24 vdc.)
TEMPERATURE RANGE—
Operating: +32°F to +140°F (0°C to +60°C)
Storage: –49°F to +185°F (–45°C to +85°C).
HUMIDITY RANGE—
5 to 99% RH, non-condensing.
OPERATING RANGE—0 to 100% LFL.
ACCURACY—
±3% of full scale over specified temperature range.
SOLID STATE OUTPUTS (Base model only)—
The outputs are open collector transistors with a 100K
resistor from the collector to emitter with the emitter
grounded, rated 100 ma at 32 volts dc maximum.
RELAY CONTACTS (Premium model only)—
Selectable normally open/normally closed contacts
rated 5 amperes at 30 vdc/250 vac. See Table 1 for
selectable relay options.
CURRENT OUTPUT (Premium model only)—
4 to 20 ma dc current, with a maximum loop resis-
tance of 600 ohms at 20 to 32 vdc.
INSTRUCTIONS
Combustible Gas Controller
R8471A
©Detector Electronics Corporation 1995 2/95 95-8398-02
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