Alpha Omega Instruments Portable Oxygen Analyzer Series 3520

 The Series 3520 Portable Trace Oxygen Analyzer is battery-operated and designed for industrial and commercial applications where accurate and reliable spot trace oxygen measurements are needed. The Series 3520 features Alpha Omega Instruments’ long life ambient temperature electrochemical sensor. The enclosure is made from durable polycarbonate and is rated NEMA 1 for general purpose service. The instrument is powered from rechargeable NICAD batteries that are mounted internal to the analyzer. Recharging of the batteries is accomplished using a built-in battery charger with a universal AC adapter. Single measurement ranges are available from 0-10 PPM to 0-20,000 PPM with values displayed on a front panel liquid crystal display (LCD). Options include pressure regulators, flow meters, in-line filters, pumps, and block & bleed bypass sampling systems.


Alpha Omega Instruments Portable Oxygen Analyzer Series 3520


High Performance Trace Oxygen Sensor

The Series 3520 Portable Oxygen Analyzer features a long-life ambient temperature electrochemical sensor that has a functional life of up to three times that of most “fuel cell” type sensors.

The enhanced mechanical design of the sensor ensures longer life, and virtually eliminates leakage of caustic electrolyte, a nagging (and expensive) problem associated with sensors that require periodic electrolyte maintenance. And, because the sensor is sealed, it is not position sensitive. In addition, unlike some electrochemical sensors, Alpha Omega Instruments readings from the Series 3250 do not require manual adjustment based on changes in the molecular weights of the sample gas i.e. helium, hydrogen, etc. a major advantage for continuous measuring applications. The output from the sensor is both linear and temperature compensated to provide optimum performance.

CO2 Resistant

A nemesis for any conventional “fuel cell” type trace oxygen analyzer is its inability to measure oxygen in gases containing carbon dioxide. Carbon dioxide reacts with potassium hydroxide electrolyte to form carbonic acid and in short time destroys the sensor. Not anymore. Alpha Omega Instruments offers an optional CO2 tolerant trace oxygen sensor with proprietary electrolyte. The CO2 tolerant sensor is capable of providing accurate trace oxygen readings in gases containing up to 100% carbon dioxide without shortening the life of the sensor.

Made in the USA

The Series 3250 is priced significantly less than most other manufacturers, and it is manufactured as well as quality control tested here in the United States. In fact, our product quality is emphasized throughout the manufacturing process starting with raw material vendor surveys through final assembly, testing, and system calibration. We’ve also earned an exceptional reputation for presale and after-market support for over 25 years.


  • State-of-the-Art Sensor Technology : High Precision Measurements
  • Light Weight/Compact Design : Easy to Carry and Transport
  • Rapid Speed of Response : Senses Oxygen Changes in Seconds
  • Built-in NICAD Batteries : Provides Hours of Continuous Operation
  • Uses Standard NICAD’s : Replacement Batteries Found World-Wide
  • Minimum Maintenance : Low Cost of Ownership



  • Measurement Ranges (parts per million) 0-10, 0-50, 0-100, 0-200, 0-500, 0-1,000, 0-5,000, 0-10,000, and 0-20,000
  • Accuracy¹: + 1% of full scale. ¹Stated at constant temperature and pressure
  • Linearity: + 1% of full scale.
  • Response Time: 90% of full scale response in less than 10 seconds (typical). The response time for ranges of 0-50 PPM or less depend to a great extent on the design of the sample delivery system including the materials used.
  • Sensor Type: Long-life Ambient Temperature Electrochemical Sensor (Optional CO2 Resistant Sensor Available).
  • Temperature Compensation: Standard.
  • Operating Temperature Range: 40° to 104° F (5° to 40° C)
  • Warranty: Two years electronics one year sensor.


  • Display: 3-1/2 digit liquid crystal display (4-1/2 digit for the 0-5,000, 0-10,000, and 0-20,000 ppm range instruments.
  • Input Power: Powered from eight AA Rechargeable NICAD batteries with built-in universal AC battery charger.
  • Analog Output: No analog output.

Sample Gas Characteristics

  • Sample Flow Rate: 1.0 to 2.0 standard cubic feet per hour (SCFH). 0.5 to 1.0 liters/ minute (LPM).
  • Sample Gas Temperature: 40° to 104° F (5° to 40° C)
  • Sample Gas Pressure Limits: 0.1 to 1.5 psig (0.007 to 0.1 kg/cm2).
  • Entrained Solids: <3 mg/ft³: no in-line filter required >3 mg/ft³: in-line filter is required
  • Hydrocarbon Mist: <0.7 mg/ft³: no in-line filter required >0.7 mg/ft³: in-line filter is required


  • Enclosure: Polycarbonate rated NEMA 1.
  • Dimensions: 6.5 inches (165.1 mm) height 6.5 inches (165.1 mm) width 7.8 inches (196.9 mm) height Note: All dimensions are without optional equipment
  • Gas Connections: 1/4″ stainless steel compression fittings.

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