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GDC-150 Operation Manual
4.2. Detecting Gas
Upon detection of the presence of target gas, the signal output increases to a value
equal to the amount of gas being detected by the sensor. If the LED display option
has been supplied, this value will be displayed. If the concentration of gas is above
the preset alarm threshold, the outer LED changes to red, the alarm relay de-
energizes and the amber relay coil LED goes out.
As the detected gas level subsides, the output signal will decrease again to a value
equal to anything being detected by the sensor and this will be indicated on the LED
display (if this option has been selected). The relay will automatically reset after the
signal drops below the set point value.
4.3. System Failure
In the event of a system failure, the outer LED will flash red, the relay will de-energize,
the relay coil LED will go out and the output signal will drop below 4.0 mA. A failure
can consist of a burned out sensor element (solid-state or catalytic), a failed or
damaged component on the circuit board, or a wiring-related problem.
4.4. Sensor Notes
Sensor Type
Solid-State
(Refrigerant)
Solid-State
(Combustible)
Catalytic
(Combustible)
Electrochemical
(E.g., Oxygen)
10
Sensors require lengthy warm up and stabilization time after installation. Do not
perform any calibration functions until the sensors have been operating for at least 24
hours.
14
10
• Not gas specific
• Respond to a fairly wide range of interfering gases and
vapors
•
Temperature and humidity compensated to reduce drift in
environments where these values change regularly
• Not gas specific, but are less likely to suffer from false
alarms from interfering gases (due to the extremely high
measuring range for which they have been calibrated)
• Specific to combustible gases and vapors
• Temperature compensated
• These sensors are quite gas specific
• Will respond to some other gases (see cross sensitive
gases table on page 7 for more information)
• Temperature compensation to reduce drift in environments
where the temperature changes regularly
Operation Notes
5209-9000 Rev 0
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