Alphasense O2-C3 Electrochemical Oxygen Sensor
| Brand | Alphasense (UK) |
|---|---|
| Origin | United Kingdom |
| Model | O2-C3 |
| Measurement Range | 0–30% O₂ |
| Operating Life | >3 years |
| Dimensions | Φ20.3 × 23 mm |
| Output Current | 65–85 µA @ 22°C, 20.9% O₂ |
| Response Time (t₉₀) | <45 s |
| Linearity Error | ±0.6 ppm |
| Weight | <18 g |
| Operating Temperature | −30 to +55°C |
| Operating Pressure | 80–120 kPa |
| Relative Humidity Range | 5–95% RH (non-condensing) |
| Storage Stability | 6 months |
| Load Resistance | 47–100 Ω |
Overview
The Alphasense O2-C3 is a high-stability, diffusion-limited electrochemical oxygen sensor engineered for continuous, low-power monitoring of ambient or process oxygen concentrations in industrial safety, environmental instrumentation, and portable gas detection systems. Based on a three-electrode electrochemical cell architecture with an aqueous alkaline electrolyte, the O2-C3 operates via the cathodic reduction of molecular oxygen at a gold working electrode, generating a linear current output proportional to the partial pressure of O₂ in the sampled gas phase. Its robust construction—featuring a hydrophobic PTFE membrane and integrated thermal compensation—ensures stable performance across variable temperature and humidity conditions without requiring external calibration gases during routine operation. Designed to meet the demanding requirements of fixed and portable analyzers, the O2-C3 complies with IEC 60079-29-1 for use in potentially explosive atmospheres when integrated into certified equipment.
Key Features
- Wide measurement range of 0–30% O₂ by volume, suitable for both normoxic and hypoxic/hyperoxic environments
- Long operational lifetime exceeding 36 months under typical indoor ambient conditions (20–25°C, 40–60% RH)
- Fast t₉₀ response time of less than 45 seconds, enabling timely detection in dynamic gas environments
- Low power consumption: operates passively without excitation voltage, delivering microampere-level current output directly proportional to O₂ concentration
- Compact cylindrical form factor (Φ20.3 × 23 mm) with standardized pin layout for seamless integration into OEM gas modules and analyzer PCBs
- Thermally compensated design minimizes drift across −30°C to +55°C operating range; no external temperature sensor required for basic applications
- Stable baseline and repeatability supported by factory calibration traceable to NIST-traceable reference standards
Sample Compatibility & Compliance
The O2-C3 is optimized for sampling clean, dry to moderately humid air and inert carrier gas mixtures. It exhibits minimal cross-sensitivity to CO₂, CO, NO₂, SO₂, and H₂S (<±2% full-scale reading), making it suitable for multi-gas instruments where oxygen correction is critical. The sensor is not recommended for direct exposure to condensing moisture, organic solvents, or high concentrations of acidic or reducing gases without appropriate pre-filtration. In terms of regulatory alignment, the O2-C3 supports system-level compliance with EN 45544-1 (workplace gas detectors), ISO 12032 (oxygen deficiency warning devices), and UL 2075 (gas and vapor detectors). When incorporated into medical-grade analyzers, it may contribute to adherence with IEC 62304 (software lifecycle) and ISO 13485 (quality management), subject to full system validation.
Software & Data Management
As a passive analog transducer, the O2-C3 outputs a linear current signal (65–85 µA at 20.9% O₂, 22°C) that interfaces directly with standard current-to-voltage conversion circuits (e.g., transimpedance amplifiers) on host instrument PCBs. No embedded firmware or digital communication protocol is present—data acquisition and linearization are performed externally. For calibrated output, users apply a two-point span/zero adjustment using certified gas standards (e.g., zero air and 20.9% O₂ in N₂). Advanced implementations integrate temperature compensation algorithms (based on onboard thermistor readings) and humidity correction models per ISO 8573-1 Annex B. While the sensor itself does not support FDA 21 CFR Part 11 audit trails or GLP/GMP electronic record features, its predictable metrological behavior enables full traceability when paired with validated data logging hardware and SOP-controlled calibration procedures.
Applications
- Fixed and portable oxygen deficiency monitors in confined space entry systems (mining, tunneling, shipbuilding)
- O₂ feedback control in inert gas blanketing systems for petrochemical storage tanks and reactors
- Process oxygen monitoring in steelmaking off-gas analysis and combustion optimization
- Benchtop and handheld gas chromatography (GC) and mass spectrometry (MS) auxiliary detectors
- Medical ventilator and anesthesia workstation O₂ concentration verification modules
- Environmental chambers and controlled atmosphere storage for food and pharmaceutical logistics
FAQ
What is the recommended load resistance for optimal linearity?
A load resistance between 47 Ω and 100 Ω is specified to maintain output stability and minimize voltage drop-induced nonlinearity.
Can the O2-C3 be used in high-humidity environments?
Yes—continuous operation is supported at 5–95% RH (non-condensing); prolonged exposure to saturated conditions may accelerate electrolyte loss and reduce service life.
Does the sensor require periodic recalibration?
Field recalibration is recommended every 6–12 months depending on exposure history and accuracy requirements; initial factory calibration remains valid for up to 6 months in sealed storage.
Is the O2-C3 compatible with hazardous area certifications?
The sensor itself is not intrinsically safe; however, it is routinely integrated into ATEX/IECEx-certified gas detectors as a component-level element meeting Clause 8.3 of IEC 60079-29-1.
How does pressure variation affect measurement accuracy?
Output is proportional to O₂ partial pressure; measurements remain accurate within 80–120 kPa absolute pressure range—outside this band, barometric compensation must be applied in software.
