AlphaSense O2-A3 Oxygen Sensor

O2-A3 oxygen sensor
Regular price $39.00 USD Sale price

Compare at $69.00 USD

POs or wholesale quantity discounts click here

The AlphaSense O2-A3 oxygen sensor is a plug-in replacement sensor for hand-held gas detectors that use an O2-A3 sensor. 

Verify the sensor you are replacing has AlphaSense O2-A3 printed on the side before ordering. Due to our low prices we cannot accept returns for the wrong sensor.


  • 0.1 to 20.9% oxygen sensor
  • Does not require calibration
  • Up to 3 year lifespan
  • Small, compact and maintenance free

The EC board and development kit converts the sensor’s analog output current to a voltage that is measured by a high-resolution analog to digital converter. The digital voltage is corrected and compensated for temperature and pressure by a microcontroller to produce an accurate gas concentration measured in ppm (parts per million). This can be read as serial UART output or can be logged in internal memory for later retrieval. In addition the board makes it easy to apply zero or span calibration.


AP-0004 O2-A3 Sensor – Plug-in replacement sensor for many oxygen safety monitors or for integration into OEM oxygen safety products.

CM-32921 O2-A3 Sensor Development Kit  Easy to use, simply plug the EC board into your PC via the included Serial UART to USB cable. Use our free GasLab® software to measure and graph oxygen levels, barometric pressure, temperature, and % relative humidity. Includes on-board memory for data logging.

CM-32920 O2-A3 Sensor EC Board – Same functionality as the development kit without USB cable or software.


  • Measurement Range: 0.1-20.9% Oxygen
  • Output @ 20.9% Oxygen: 60-85 uA
  • Output @ 0% O2: < 2.5 uA
  • Response Time: < 15 sec. t90 (s) from 20.9% to 0%
  • Linearity: 0.6% O2 deviation @ 10%
  • Output drift: < 1% change @ 3 months
  • Operating life: > 36 months until 85% original Output of 20.9%
  • Analog Output: 0-3VDC

Smart EC Board Functionality Adds

  • Temperature, %RH Sensor
  • Barometric Pressure Sensor
  • 64K memory for time-stamped data logging of all measurements
  • Serial UART output
  • RS485 output with optional RS485 cable

Development Kits Adds

  • Serial UART to USB cable
  • Free Windows software for real-time measurements, graphing


  • Dimensions (sensor): 17.4mm x 20.3mm
  • Dimensions (sensor + PCB): 40mm X 25mm x 29mm (LxWxH)
  • Power Input: 3.3-5.5 VDC
  • Current Consumption: 10ma peak, < 3mW average


Free Easy-to-use GasLab® Software

The Devkit uses GasLab® software for setup, calibration, data logging, and real-time data analysis via USB. GasLab® makes it easy to export data into a .CSV file that can be imported into any industry-standard software or spreadsheet. GasLab® runs on Windows XP or higher, and free to use with our products.

Download Software

System Requirements

  • Windows XP SP2 or newer
  • Microsoft .Net 3.5 Runtime Libraries

Tube cap adapters easily convert 20mm standard gas sensors from diffusion to sampling sensors. Molded polymer grips sensor for easy fit and removal while maintaining a good seal.

RS485 Cable. Custom USB cable enables RS485 communication to GasLab Software for EC Sensor Board and Development Kit.

Micro-Pump Kit includes all the tools you need to urilize the tube-cap adapters as part of a sampling sensor system.

Nafion tubing is a highly selective, semi-permeable membrane to water vapor. If gases inside Nafion tubing are wetter than gases surrounding the tubing, drying will occur. If the surrounding gases are wetter, humidification will occur.

Micro gas sampling pumps provide a constant flow of air across the sensor with a tube cap - perfect for bench-top testing of sensors for closed-loop sampling applications.

Customer Reviews

Based on 5 reviews
replaced my bacharach o2
Great service
Replacement Oxygen Sensor

"Swift response and shipment. The product is easy to setup and use. It is just what I was looking for."

- Shima Tomohiro

Read More Reviews...