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GT823 Oxygen Deficiency/Enrichment NOVA-Sensor Standalone Unit

Product Literature

  • General Purpose or Non-Hazardous Application
  • Standalone Unit
  • Electrochemical Sensor
  • 3-digit Digital Display
  • 4-20 mA Output
  • Relay Contacts
  • 2 Alarm Set Points
  • Built-in Horn and Strobe
  • Operates on Standard 120 or 240 Volt Power Source


Features and Benefits

  • Oxygen Detector
  • One-piece construction for general purpose use
  • Maintenance free electrochemical cell sensing element in stainless steel housing
  • Operates on standard 120 or 240 volt power source
  • 4-20 mA output for optional connection to external equipment
  • User programmable LOW alarm and HIGH alarm set points
  • Voltage-free dry contacts for local control
  • Available two piece model allows for sensor to be located remotely
  • Digital readout of oxygen concentration to ±0.1% resolution
  • Pushbutton switch initiates “one-man” calibration sequence
  • Pushbutton switch to silence horn
  • Combination 105dB(A) high output alarm horn sounder & 5 joule xenon strobe
  • Shipped fully assembled and pre-calibrated
  • 5 Year Warranty
  • Made in USA
  • Typical applications include but not limited to laboratories, medical facilities, testing facilities, semiconductor manufacturing, and locations where carbon dioxide or nitrogen gases are used

Product Summary

The SST Model GT823 Oxygen Sensor includes a high reliability microprocessor based transmitter/controller, built-in sensor, relays , audible and visual alarm in a one-piece construction.  Monitors the level of oxygen within an area.  For general purpose use.  5 Year Warranty.  Made in the U.S.A.


The SST Model GT823 Oxygen Deficiency/ Enrichment NOVA-Sensor® is a completely self-contained device that measures and displays the concentration of oxygen present in a protected area, performs local control functions, and optionally transmits this information to a central control point. Two alarm relays and a fault relay are included.

An electrochemical fuel cell sensing element with a patented diffusion barrier is located inside the stainless steel flameproof housing. The three electrode cell is maintenance free and stable over long periods of time. The capillary diffusion barrier technology results in a direct response to volume concentration. A high reserve of electrochemical activity insures a long life and excellent temperature stability. The performance is relatively unaffected by humidity, provided that conditions are noncondensing.

Each SST NOVA-Sensor includes a high reliability microprocessor based transmitter/ controller in the associated explosion proof housing. A digital readout continuously displays operating status and the actual concentration of oxygen. The transmitter converts this reading to a standard 4-20 mA signal. This signal may be connected to any remote device with a standard 4-20 mA input. The HIGH and LOW alarm relays operate at user adjustable alarm trip points; either relay may be set to operate above or below the normal oxygen level. The fault relay operates upon loss of power or internal failure of the unit. Relays are suitable for controlling local HVAC or equipment shutdown.

The automatic calibration sequence is easily completed by just one person. The microprocessor stores the results of the calibration in its permanent (non-volatile) memory for use in subsequent operation. There are no screwdriver or other manual adjustments required. During the calibration process, the 4-20 mA and relay outputs from the sensor are normally suppressed. The sensor automatically returns to normal operation when the calibration is complete. During calibration, the technician may optionally activate the built-in comprehensive input/output test sequence (Comp- Test™). During CompTest, the NOVASensor’s analog and relay outputs are not suppressed, thus providing a complete operational check of the overall system.

The Model GT823 is suitable for general purpose applications where no combustible gas are present.

Architect's and Engineer's Specifications

Oxygen deficiency/enrichment sensing capability shall be provided by electrochemical fuel cell sensors with diffusion barrier contained in a stainless steel housing. The sensing element shall be exposed to the detected gas through a suitable filter. The element shall use a capillary diffusion barrier technology which results in a direct response to volume concentration. The performance shall be relatively unaffected by humidity, provided that conditions are non-condensing. The sensor shall include microprocessor based control electronics which converts the measured gas concentration to the industry standard 4-20 mA signal, plus alarm and fault relay outputs. A continuously reading digital display shall be provided on the sensor, capable of displaying sensor status and the current oxygen concentration in percent. A switch for initiating sensor calibration shall be provided. Calibration shall not require any operator adjustment. All calibration data shall be stored in non-volatile memory in the sensor. Relay and analog outputs shall normally be inhibited during calibration; however, it shall be possible for the calibrating technician to selectively enable outputs when desired. Safety Systems Technology Model GT823 Oxygen Deficiency/Enrichment NOVA-Sensor®, or approved equivalent, shall be supplied.

Technical Specifications and Ordering Information

Technical Specifications

Power Input: 85 to 264 volts AC, 47 to 440 Hz
Operating Temperature: -22 to + 131°F (-30 to +55°C)  |  Recommended storage +32°F to +68°F
Operating Humidity: 0 to 99% Relative Humidity non-condensing
Display Resolution: 0.1%
Nominal Range: 0-25% Oxygen
Max Overload: 30% Oxygen
Output Drift: Less than 1% signal loss per month (typically less than 15% in two years)
Operating Life of Cell: 2 Years (Plug-in cell offers easy field replacement)
Relay Outputs: Low (Deficiency) alarm, High (Enrichment) alarm, Fault/Malfunction
Configurable normally open or normally closed
Relay Contact Ratings: 6 amps @28 volts DC or 300 volts AC resistive  |  1/8 HP @ 120/240 volts AC
Analog Output: 0 to 20 mA current source into a load of 600 ohms or less
Warranty: 5 Years
Country of Origin: Made in USA
Size: 8 x 17 3/4 x 6 inches (200 x 450 x 152 mm)
Weight: 14 pounds (6.4 kg)

Ordering Information

823-1 Model GT823 Oxygen Deficiency/Enrichment NOVA-Sensor Standalone Unit with built-in transmitter, sensor, relays, power supply, and audible and visual alarm
823-2 Two-piece model with remote sensor mounting

Optional Accessories

850-4 Sensor remote mounting junction box
851-1 Rain shield, stainless steel
851-5 Water spray shield for water jets/heavy seas/ dust
852-1 Dust cover
852-3 Dust cover w/ add’l charcoal filter for high silicone
867 Complete calibration kit, please specify gas when ordering