Axetris LGD HCL Series Tunable Diode Laser Gas Detection Module

Overview

The Axetris LGD HCL Series is an OEM-optimized, compact tunable diode laser (TDL) gas detection module engineered for high-selectivity, real-time quantification of hydrogen chloride (HCl) in industrial and environmental gas streams. Operating on the principle of tunable diode laser absorption spectroscopy (TDLAS), the module leverages narrow-linewidth laser emission precisely tuned to a fundamental ro-vibrational absorption line of HCl near 1.7 µm. This spectral selectivity ensures minimal interference from co-existing gases—including H₂O, CO₂, CH₄, NH₃, and O₂—enabling reliable measurement in complex matrices without optical or chemical filtering. Unlike conventional NDIR or electrochemical sensors, the LGD HCL employs a single-beam, dual-wavelength referencing scheme that eliminates the need for a physical reference cell or zero-gas calibration. Its non-contact, optical path-based architecture provides inherent immunity to sensor poisoning, drift, and electrode degradation—critical for long-term unattended operation in harsh process environments.

Key Features

• Optically based, contactless measurement with no consumables or reactive surfaces
• High specificity to HCl via targeted TDLAS at 1.7 µm, validated against ASTM E2698 and ISO 14687 interference test protocols
• Sub-2-second response time (T₉₀) enabling dynamic process feedback and rapid leak detection
• Stable baseline performance over temperature ranges from −20 °C to +60 °C ambient; optional heated probe variant supports up to 190 °C hot-gas sampling
• Modular mechanical footprint (120 × 80 × 45 mm) with standardized electrical and optical interfaces (RS-485, analog 4–20 mA, digital I²C) for seamless OEM integration
• Factory-calibrated with NIST-traceable HCl standards; no field recalibration required under normal operating conditions
• Robust aluminum housing rated IP65, suitable for indoor and outdoor enclosures per IEC 60529

Sample Compatibility & Compliance

The LGD HCL module is compatible with dry and humid gas streams containing particulate loads ≤10 mg/m³. It has been verified for continuous operation in flue gas (post-SCR, post-FGD), biogas, landfill off-gas, and HVAC duct air. The optical path design tolerates condensation-free dew points down to −10 °C; optional heated sample cell maintains measurement integrity in saturated or low-temperature applications. Regulatory compliance includes CE marking per Directive 2014/30/EU (EMC) and 2014/35/EU (LVD), RoHS 2011/65/EU, and conformity with EN 61000-6-2 (immunity) and EN 61000-6-4 (emissions). For regulated emissions monitoring, the system supports audit-ready data logging aligned with EPA Method 320 and EN 15267-3 requirements when integrated with compliant DAQ hardware.

Software & Data Management

The module communicates via ASCII protocol over RS-485 or TTL-level UART, supporting Modbus RTU for SCADA integration. Axetris provides the LGD Configuration Tool (Windows/Linux), enabling users to configure output scaling, alarm thresholds, averaging intervals (1–60 s), and diagnostic reporting (laser health, signal-to-noise ratio, path loss). Raw absorbance data and concentration values are timestamped with microsecond resolution. When deployed in GMP or GLP environments, the module can be paired with third-party data acquisition systems compliant with FDA 21 CFR Part 11 for electronic records and signatures—supporting full audit trails, user access control, and change history logging.

Applications

• Process Control: Real-time HCl monitoring in selective catalytic reduction (SCR) systems, municipal solid waste incineration (MSWI), and cement kiln exhausts to optimize reagent dosing and minimize corrosion risk
• Emissions Monitoring: Continuous compliance verification per EU IED Annex VI and US EPA 40 CFR Part 60 Subpart Da for HCl stack emissions from power plants and industrial boilers
• Environmental Monitoring: Fugitive HCl detection at landfill leachate treatment units, composting facilities, and livestock barn ventilation exhausts
• Safety & Leak Detection: Area monitoring in chlor-alkali production, PVC manufacturing, and pharmaceutical synthesis lines where HCl exposure poses acute inhalation hazards (TLV-TWA = 1 ppm)
• Indoor Air Quality (IAQ): Integration into smart HVAC controllers for acid gas event detection in laboratories, cleanrooms, and enclosed agricultural buildings

FAQ

Does the LGD HCL require periodic calibration with span gas?
No. The module uses a self-referencing TDLAS method with built-in wavelength stabilization and intensity normalization. Field calibration is not required unless subjected to extreme mechanical shock or optical contamination.
Can it measure HCl in high-moisture gas streams?
Yes—provided condensation is prevented upstream. Optional heated sample cells (up to 190 °C) and purge-air ports mitigate water vapor interference and lens fogging.
Is the module compatible with explosion-proof enclosures?
The LGD HCL itself is non-incendive (Class I, Division 2 / ATEX Zone 2 compliant when installed in certified housings). Intrinsically safe barrier integration is supported via current-loop outputs.
What is the minimum detectable concentration (MDL) under standard conditions?
The practical MDL is ≤0.2 ppm (1σ, 1-s average) in clean, dry N₂; performance in real-world matrices depends on optical path length, pressure, and background absorption.
How is traceability maintained for regulatory reporting?
Each unit ships with a factory calibration certificate traceable to NIST Standard Reference Material (SRM) 1941b, including uncertainty budget per ISO/IEC 17025 guidelines.