Axetris LGD Compact-A CH4/C2H6 Methane and Ethane Laser Gas Detection Module

Overview

The Axetris LGD Compact-A CH4/C2H6 is a high-performance, OEM-optimized laser gas detection module engineered for selective, real-time quantification of methane (CH₄) and ethane (C₂H₆) in complex gas matrices. Built upon Tunable Diode Laser Spectroscopy (TDLS), this module leverages near-infrared (NIR) absorption spectroscopy at precisely targeted molecular absorption lines—specifically the ν₃ fundamental band of CH₄ (~1653 nm) and the 2ν₃ + ν₄ combination band of C₂H₆ (~1670 nm). Unlike electrochemical or catalytic bead sensors, TDLS provides inherent spectral selectivity, eliminating cross-sensitivity to CO₂, H₂O, N₂, O₂, and other common background gases typically present in biogas, landfill off-gas, or natural gas distribution streams. Its optical, non-contact measurement architecture ensures long-term stability without sensor drift, chemical poisoning, or consumables—making it suitable for unattended operation over extended periods in demanding industrial and environmental monitoring applications.

Key Features

• OEM-integrated form factor: 32 × 32 × 12 mm compact PCB-mountable module with integrated laser diode, thermoelectric cooler (TEC), photodetector, and digital signal processing ASIC.
• Dual-gas capability: Simultaneous, independent quantification of CH₄ (0–100 ppm and 0–4% full scale) and C₂H₆ (0–1000 ppm) within a single optical path.
• Ultra-fast response: T90 ≤ 2 seconds enables dynamic process monitoring and rapid leak detection in pipeline integrity management.
• Zero calibration drift: Factory-calibrated using NIST-traceable gas standards; no field recalibration required under stable thermal and pressure conditions.
• Robust optical design: Hermetically sealed optical cavity with anti-reflective coated sapphire windows; resistant to condensation, particulates, and moderate vibration per IEC 60068-2.
• Low power consumption: <1.2 W typical operating power; compatible with 3.3 V or 5 V DC supply rails for embedded system integration.

Sample Compatibility & Compliance

The LGD Compact-A CH4/C2H6 operates effectively across gas matrices with up to 95% relative humidity (non-condensing), total pressure ranges from 700–1100 hPa (ambient to slight overpressure), and sample temperatures from −10 °C to +50 °C. It is validated for use in biogas (CH₄: 40–70%, CO₂: 30–60%, trace H₂S < 100 ppm), landfill gas, natural gas transmission lines (up to 98% CH₄), and agricultural ambient air (ppm-level CH₄ from manure lagoons or enteric fermentation). The module complies with EU directives CE (2014/30/EU EMC, 2014/35/EU LVD), RoHS 2011/65/EU, and REACH Regulation (EC) No. 1907/2006. While not intrinsically safe certified as a standalone unit, it is routinely integrated into ATEX Zone 2 or Class I, Division 2 systems by OEM partners meeting IEC 60079-0 and UL 913 requirements.

Software & Data Management

The module communicates via UART (3.3 V logic) or I²C interface, delivering ASCII or binary output frames containing raw absorbance values, temperature-compensated concentration results, diagnostic flags (e.g., laser health, signal-to-noise ratio, window contamination index), and internal sensor status. Axetris provides open-source firmware libraries (C/C++ and Python) supporting Linux, FreeRTOS, and bare-metal microcontroller platforms (ARM Cortex-M series). Data logging, alarm thresholds, and multi-point averaging are implemented at the host system level—enabling seamless integration into SCADA, PLC-based control systems, or cloud-connected IoT gateways. For regulated environments (e.g., EPA Method 21 compliance reporting or EU Industrial Emissions Directive monitoring), the module supports time-stamped, audit-trail-ready data export compatible with 21 CFR Part 11–compliant software architectures when paired with appropriate host-layer validation.

Applications

• Biogas upgrading plants: Real-time CH₄/C₂H₆ ratio monitoring to optimize membrane or PSA separation efficiency and detect hydrocarbon fouling.
• Landfill gas collection networks: Continuous emission monitoring at wellheads and flare stacks per EPA 40 CFR Part 60 Subpart WWW and EU LCP BREF guidelines.
• Natural gas distribution: Pipeline integrity verification via mobile or fixed leak detection units; odorant depletion assessment (C₂H₆ as tracer).
• Agricultural emissions research: High-temporal-resolution CH₄ flux measurements from dairy barns, anaerobic digesters, and manure storage facilities aligned with IPCC Tier 3 protocols.
• Indoor air quality & safety: Early warning of explosive gas accumulation (LEL monitoring) in confined spaces such as LNG refueling stations, compressor enclosures, and biogas engine rooms.

FAQ

Does the module require zero/span gas calibration during field operation?
No. The TDLS principle and factory calibration eliminate routine zero/span adjustments. Long-term stability is verified per ISO 12039 for gas analyzers, with typical drift <±2% FS/year under controlled environmental conditions.
Can the module measure CH₄ and C₂H₆ simultaneously in the same gas stream?
Yes. Dual-wavelength TDLS architecture enables concurrent, spectrally resolved detection without optical multiplexing or flow splitting.
Is compensation for water vapor interference included?
Yes. Integrated NDIR-based H₂O measurement (optional add-on) or external humidity input enables real-time spectroscopic water correction using Beer-Lambert law modeling.
What is the recommended sampling interface for harsh biogas environments?
A heated, particulate-filtered, and moisture-trapped sample line (e.g., 1/4″ PTFE tubing with 2 µm sintered filter and Nafion™ dryer) is advised to prevent optical window fouling and condensation.
How is traceability maintained for regulatory reporting?
Each module ships with a certificate of calibration traceable to NIST Standard Reference Materials (SRMs); optional on-site verification kits include certified CH₄/N₂ and C₂H₆/N₂ gas standards per ISO 6141.