Alphasense O2-A2 O2-A3 Electrochemical Oxygen Sensor

Alphasense O2-A2 O2-A3 Electrochemical Oxygen Sensor

Parameters

Brand: Alphasense
Model: O2-A2 O2-A3
Origin: UK

O2-A2
Measurement range: 0 – 30% VOL O₂ (standard air 20.9%)
Output sensitivity: 22°C normal temperature, 20.9% O₂: 80 – 120 μA
Zero current (in nitrogen): < 2.5 μA, zero drift is extremely small
T90 response time: typical < 8s, maximum ≤ 15s (20.9% → 0% switch, matching 47Ω load)
Linear error: full range < 0.6% O₂, high and low oxygen sections have stable accuracy
Recommended load resistance: 47 – 100 Ω (voltage sampling from voltage divider)
Service life: > 24 months (output decays to initial 85% to determine the end of service life)
3-month long-term drift: output change < 1%, excellent stability Alphasense

Environmental tolerance specifications
Operating temperature: -30℃ ～ +55℃
Pressure range: 80～120 kPa (constant pressure fluctuations are compatible)
Humidity: 5～95% RH (no condensation; short-term can tolerate 99% RH)
Interference:
CO₂ sensitivity: 0.1% reading change / 1% CO₂ (5% CO₂ environment)
Pressure sensitivity: <0.1% output change / 1% pressure fluctuation
Humidity interference: Large fluctuations in temperature and humidity only cause a <0.7% O₂ reading offset
Storage conditions: Store sealed at 3～20℃, maximum storage time 6 months (open circuit preservation)
Physical dimensions and structure
Appearance: Cylindrical package, diameter 20.0mm, height 17.4mm (including top foam filter membrane)
Weight: < 16g
Pins: Dual-pin design (positive and negative poles, no third reference pole), downward plug-in type installation
Patented leak-proof sealing structure to prevent electrolyte leakage and damage to the motherboard
Circuit Wiring and Sampling Key Points
Connect two pins in series to fix the load resistor (preferably 47Ω);
The voltage across the resistor = sensor current × load resistor, sent to the ADC for collection;
Example: 100μA × 47Ω = 4.7mV (corresponding to 20.9% oxygen voltage)
No power supply is required; the sensor generates a microcurrent on its own; do not directly connect to a voltage source, as it will permanently burn out.
The recommended accessory circuit should add a low-pass RC filter to suppress the reading jumps caused by air flow disturbances.

O2-A3
Core electrical performance (standard air at 22℃, 20.9% O₂)
Measurement range: 0 – 30% VOL O₂
Output sensitivity: 55 – 85 μA (lower than 80 – 120 μA of A2, with smaller current and slower long-term attenuation) Alphasense
Zero current (nitrogen): < 2.5 μA, extremely low zero point
T90 response time: ≤ 15 s (47Ω load, 20.9% → 0% switch)
Linear error: < 0.6% O₂ throughout the range
Recommended load resistance: 47Ω – 100Ω, voltage sampling with voltage division
Nominal service life: > 36 months (3 years), output decays to 85% of initial value to determine the end of life (A2 only 24 months)
Long-term stability: 3-month output drift < 2%, superior to A2’s long-term stability
Environmental tolerance parameters
Operating temperature: -30℃ ～ +55℃
Air pressure: 80～120 kPa
Humidity: Continuous 5～95% RH, short-term can withstand 99% RH (no condensation)
Interference indicators:
CO₂ sensitivity: 0.1% reading change / 1% CO₂ (5% CO₂ condition)
Humidity influence: Error caused by full range of temperature and humidity fluctuations is <0.7% O₂
Air pressure sensitivity: <0.1% output change / 1% air pressure fluctuation
Storage conditions: Sealed and protected from light at 3～20℃, longest storage time is 6 months (open circuit preservation)
Physical structure and hardware compatibility
Appearance: cylindrical, diameter 20.3mm, total height 17.4mm, weight < 16g
Pins: double pin with two terminals (positive / negative, without reference terminal), exactly the same as O2-A1, O2-A2 pins and mounting holes, can be directly replaced without modifying the PCB
Patented leak-proof sealing structure, significantly reduces electrolyte loss rate, suitable for long-term online equipment
Circuit acquisition scheme (common to A2)
The two poles of the sensor are connected in series with a 47Ω standard load resistor;
The voltage across the resistor = sensor current × Rload;
For example: 70μA × 47Ω = 3.29mV (corresponding voltage for 20.9% oxygen)
The RC low-pass filter at the back end eliminates fluctuations caused by airflow;
Do not directly connect to the power supply voltage, as it will permanently damage the sensor.
Application scenarios (mainly featuring long-term maintenance-free equipment)
Industrial fixed online monitoring: long-term oxygen content alarmers in pipe galleries, enclosed spaces, boiler rooms, and sewage ponds
Fixed detectors for HVAC / building fresh air and underground garages (3-year no-replacement, reducing operation and maintenance)
Fixed safety monitoring equipment for ships, ship cabins, LNG storage tanks, and underground environments
Long-term online monitoring of oxygen concentration in oxygen generation equipment and laboratories
Cold chain storage, fresh air controlled storage facilities, and oxygen content monitoring of gas pipelines