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The Nova 325 Portable Trace Oxygen Analyzer is designed for accurately measuring trace PPM oxygen in clean, dry sample gas.

The customer replaceable electrochemical sensor produces a small output current directly proportional to the amount of O2 in the sample and is capable of measuring trace PPM levels of O2 in any range from 0-100 to 0-9999 PPM. The lowest readable level is 1 PPM.

Bypass solenoid valves are used to trap low PPM oxygen in the O2 cell to avoid exposure to ambient air. This allows for a rapid purge down and also protects the cell from momentary over exposure to high O2 levels.

A flow control valve and flow meter are provided for regulating the flow of samples under positive pressure. A built-in sample pump is provided for use on samples under atmospheric or slight negative pressure.

A rechargeable battery provides enough power for the pump and electronics for about 20 hours of continuous opertion. The analyzer may still be operated while it is being charged. A red LED indicates when to recharge the analyzer and a green LED indicates that it is receiving recharging power. The battery recharger is included with the analyzer.

Unit of Measure


Method of Detection

N/A Low range electrochemical O2 sensor

Ranges Available

N/A 0-100 PPM to 0-9999 PPM O2



Accuracy & Repeatability

N/A ±2% of reading


N/A ±1% of full scale per week

Response Time (T-90)

N/A O2 sensor may require an initial purge down from air to low PPM O2, which may last up to 6 hours. After purge down, T-90 response from 1000 to 100 PPM is 30 seconds.

Ambient Temperature Range

N/A 0-50 ºC32-122 ºF


N/A ±2% of full scale

Size & Weight

N/A 8" W x 9 1/2" H x 10" D @ 12 lbs. (20 x 23 x 25 cm @ 5.5 kg)


N/A AC/DC operation. 115 VAC 60 Hz for recharging (Other voltages available)

Output Options

N/A 0-1V or 4-20mA (optional)


N/A One high or low O2 alarm (optional)

Hazardous Area Rating Options

N/A General Purpose, Non-Hazardous


N/A For high accuracy analysis of trace PPM oxygen (O2) in non-corrosive process gas.



  • Rugged design that is light weight, compact and easy to operate
  • Fast warm-up and response
  • Accurately measures PPM O2 in gases including those containing hydrocarbons
  • any range between 0-100 to 0-9999 PPM available
  • Customer replaceable electrochemical 'fuel cell' O2 sensor
  • Blocking solenoid valves used to trap PPM O2 in cell for quick purge down and also protects cell during initial sample line purge
  • Comes complete with flow control valve, filters and flow meter
  • Digital meter readout with backlight
  • Rechargeable battery operation



  • Recorder outputs of 0-1V or 4-20 mA
  • Sampel pre-cooler for hot samples
  • Condensate removal for wet applications
  • Built-in sample pump or pressure regulator
  • AC only power operation
  • O2 alarm with LED
  • Detachable data logger
  • Type 'K' suitcase style cabinet



  • Analyzed calibration gas of O2 free nitrogen N2 for zero
  • Analyzed calibrationg gas of PPM O2 in N2 for span

Unique Applications

N/A The PPM O2 sensor in Model 325 can be affected by the presence of other gases such as H2S.

All Nova analyzers are built using proven technologies and techniques. If this product does not suit your application, please contact Nova. In many cases, we are able to build an analyzer specific to your needs.

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