Alphasense LFO2-A4 Lead-Free Electrochemical Oxygen Sensor
| Brand | Alphasense (UK) |
|---|---|
| Origin | United Kingdom |
| Model | LFO2-A4 |
| Measurement Range | 0–30% O₂ |
| Operating Lifetime | ≥5 years |
| Dimensions | Ø20.3 × 16.5 mm |
| Output Current | 80–130 µA @ 20.9% O₂ |
| Response Time (t₉₀) | <17 s (20.9% → 0% O₂) |
| Linearity Error | <0.1% O₂ at 10% O₂ |
| Weight | <6 g |
| Operating Temperature | −30 to +50 °C |
| Pressure Range | 80–120 kPa |
| Humidity Range | 5–95% RH (non-condensing) |
| Storage Life | 6 months at 3–20 °C |
Overview
The Alphasense LFO2-A4 is a high-stability, lead-free electrochemical oxygen sensor engineered for continuous ambient oxygen monitoring in industrial safety, environmental instrumentation, and portable gas detection systems. Based on a robust three-electrode electrochemical cell architecture, the LFO2-A4 operates via diffusion-controlled oxidation of oxygen at the working electrode, generating a linear current output proportional to partial pressure of O₂ in the sampled gas. Unlike conventional lead-based sensors, the LFO2-A4 eliminates toxic lead components while maintaining long-term baseline stability and low temperature coefficient — critical for applications requiring regulatory compliance with RoHS, REACH, and WEEE directives. Its sealed, membrane-diffusion design ensures consistent performance across variable humidity and moderate pressure fluctuations, making it suitable for integration into fixed gas analyzers, confined-space monitors, and medical-grade respiratory equipment where trace-level repeatability and fail-safe reliability are mandated.
Key Features
- Lead-free electrochemical cell compliant with EU environmental regulations (RoHS/REACH)
- Extended operational lifetime of ≥5 years under typical ambient conditions (20.9% O₂, 23°C, 50% RH)
- High signal linearity: deviation <0.1% O₂ at 10% O₂ concentration, supporting accurate calibration traceability
- Rapid t₉₀ response time of <17 seconds when transitioning from air (20.9% O₂) to nitrogen-purged zero gas
- Compact cylindrical form factor (Ø20.3 × 16.5 mm) optimized for PCB-mount integration and space-constrained enclosures
- Wide operating envelope: −30 to +50 °C ambient temperature; 80–120 kPa total pressure; 5–95% RH non-condensing humidity
- Low power consumption — compatible with battery-operated and intrinsically safe (IS) circuit designs
Sample Compatibility & Compliance
The LFO2-A4 is designed for direct sampling of ambient air or process gas streams containing oxygen concentrations between 0 and 30% v/v. It exhibits minimal cross-sensitivity to common interferents including CO₂ (±0.2% O₂ error at 5% CO₂), CO (<0.05% O₂ shift at 1000 ppm), and NO₂ (<0.1% O₂ shift at 5 ppm). The sensor complies with IEC 60079-29-1 for flammability risk assessment in hazardous areas and meets functional safety requirements aligned with SIL 2 per IEC 61508 when integrated into certified gas detection systems. Its construction materials and sealing methodology conform to ISO 9001 manufacturing controls, and batch-certified calibration data (including zero and span drift rates) are supplied with each production lot to support GLP-compliant instrument qualification.
Software & Data Management
While the LFO2-A4 is an analog current-output sensor (4–20 mA or 0–5 V conditioning optional), its signal characteristics are fully compatible with industry-standard gas analyzer firmware stacks. When paired with Alphasense’s recommended signal conditioning circuitry (e.g., low-noise transimpedance amplifier + 24-bit ADC), the sensor supports digital compensation algorithms for temperature and pressure variations — enabling real-time compensation per ISO 8573-1 Annex B methodologies. Raw output data can be logged and validated using third-party platforms compliant with FDA 21 CFR Part 11 (e.g., LabVIEW DAQmx, Siemens Desigo CC, or custom SCADA implementations), provided audit trail functionality and electronic signature protocols are implemented at the system level.
Applications
- Fixed and portable oxygen deficiency/enrichment monitors for confined space entry (OSHA 1910.146, EN 50104)
- Oxygen analyzers in inert gas blanketing systems for petrochemical storage tanks and semiconductor fabrication tools
- Process control sensors in steelmaking off-gas analysis (BOF/LD converters) and combustion optimization loops
- Medical ventilator and anesthesia gas module O₂ verification channels (IEC 60601-1, ISO 80601-2-12)
- Environmental monitoring stations measuring atmospheric O₂ trends for carbon cycle research
- Fire suppression system integrity verification (e.g., FM-200, Novec 1230) via continuous O₂ depletion tracking
FAQ
What is the recommended calibration frequency for the LFO2-A4 in continuous operation?
For critical safety applications, quarterly zero-and-span calibration against NIST-traceable gas standards is advised; for less demanding monitoring roles, semi-annual verification suffices.
Can the LFO2-A4 be used in high-CO₂ environments such as biogas upgrading facilities?
Yes — its documented CO₂ cross-sensitivity is ≤±0.2% O₂ at 5% CO₂, well within acceptable tolerance for most biogas O₂ monitoring specifications (e.g., EN 15439).
Does the sensor require external temperature compensation?
While the LFO2-A4 incorporates internal thermal stabilization, optimal accuracy requires external temperature measurement (±0.5°C) and application of the manufacturer-provided polynomial compensation coefficients.
Is the LFO2-A4 suitable for use in intrinsically safe (IS) barrier circuits?
Yes — its maximum open-circuit voltage (0.8 V) and short-circuit current (<200 µA) fall within Entity Parameter limits for Class I, Division 1 / Zone 1 IS approvals when used with appropriate galvanic isolators.
How does storage duration affect post-storage performance?
Storage beyond 6 months at >20°C accelerates electrolyte evaporation; units stored longer than specified must undergo full functional requalification including zero stability and response time verification before deployment.
