SIGAS Silarex Multi-Component NDIR Gas Sensor Module
| Brand | SIGAS (Schütz Mess- und Regeltechnik) |
|---|---|
| Origin | Germany |
| Model | Silarex |
| Detection Principle | Dual-Beam Non-Dispersive Infrared (NDIR) |
| Measurement Range | CO₂ up to 20 vol.%, CO up to 1000 ppm, NO up to 2000 ppm, SO₂ up to 1000 ppm |
| Response Time (T90) | < 8 s @ 0.7 L/min |
| Repeatability | ≤ ±1 % FS |
| Linearity Error | ≤ ±1 % FS (standard), ≤ ±1.5 % FS (select versions) |
| Stability | < ±2 % FS over 1000 h |
| Operating Temperature | 0–40 °C (up to 45 °C with thermostatic housing) |
| Storage Temperature | −20–60 °C |
| Humidity | 0–95 % RH (non-condensing) |
| Pressure Range | 800–1150 mbar |
| Flow Rate | 0.2–1.0 L/min (stable) |
| Warm-up Time | < 2 min (cold start), < 30 min (full thermal stabilization) |
| Power Supply | 24 VDC ±0.3 V |
| Max. Current Draw | 1.5 A (heating chamber active) |
| Heating Setpoint | 42 °C (sensor core), 45 °C (with aluminum thermostatic housing) |
| Digital Interface | Modbus ASCII/RTU over TTL, auto-baud & auto-frame |
| Gas Inlet | 3 mm ID / 5 mm OD tubing connection |
| Optical Cell | Gold-coated reflective chamber |
| Cross-Interference Suppression | Engineered spectral deconvolution and multi-wavelength compensation |
| Zero-Point Resolution | CO₂ 0.01 vol.%, CO 0.1 ppm, NO 1 ppm, SO₂ 1 ppm |
| LOD | CO₂ 0.1 %FS, CO 0.5 %FS, NO 1 %FS, SO₂ 1 %FS |
Overview
The SIGAS Silarex is a high-performance, multi-component infrared gas sensing module engineered for continuous, real-time quantification of key industrial gases—including carbon dioxide (CO₂), carbon monoxide (CO), nitrogen oxides (NO), and sulfur dioxide (SO₂)—in complex ambient or process streams. It operates on the physical principle of dual-beam non-dispersive infrared (NDIR) absorption spectroscopy: each target gas exhibits unique, narrow-band infrared absorption features—its molecular “fingerprint”—within the mid-infrared region (typically 2–14 µm). The Silarex employs matched optical paths—one through the sample cell, one through a sealed reference—to actively compensate for source drift, window fouling, and detector aging. This architecture ensures long-term baseline stability without requiring frequent zero/span recalibration. Unlike electrochemical or metal-oxide semiconductor sensors, the Silarex contains no consumable elements, catalytic surfaces, or reactive electrolytes; its optical measurement path is inherently immune to chemical poisoning, mechanical wear, or humidity-induced signal hysteresis.
Key Features
- Dual-beam NDIR architecture with gold-coated reflective gas cell for enhanced signal-to-noise ratio and minimized stray light interference
- Integrated aluminum thermostatic housing maintaining sensor core at 42 °C (or 45 °C with housing), suppressing thermal drift across ambient temperature fluctuations (0–40 °C operating range)
- Real-time temperature and pressure compensation algorithms compliant with ISO 12039 and ASTM D6522 for accurate volumetric concentration reporting under variable process conditions
- Modbus ASCII/RTU digital output over TTL interface with auto-baud detection (2400–115.2 kbps) and auto-frame synchronization—designed for seamless integration into PLCs, SCADA systems, and IIoT gateways
- Low-maintenance design: no moving parts, no consumables, no periodic electrolyte replacement—validated for >1000 h of continuous operation with < ±2 % FS drift
- Optimized flow dynamics: calibrated for stable gas delivery between 0.2–1.0 L/min via standardized 3 mm ID / 5 mm OD inlet tubing; T90 response < 8 seconds at 0.7 L/min
Sample Compatibility & Compliance
The Silarex is designed for use in clean, dry, non-corrosive gas matrices typical of combustion exhaust monitoring, biogas upgrading, indoor air quality (IAQ) control, and industrial safety applications. Its gold-coated optical chamber resists oxidation and condensation-related attenuation, supporting operation in environments with up to 95 % relative humidity (non-condensing). While not rated for direct exposure to aggressive halogenated compounds or high-concentration acidic vapors (e.g., >50 ppm HCl or HF), it complies with EN 50104 (gas detectors for CO) and meets electromagnetic compatibility requirements per EN 61326-1. For regulated environments—such as pharmaceutical cleanrooms or food processing lines—the module supports audit-ready data logging when paired with compatible controllers implementing FDA 21 CFR Part 11-compliant firmware (user-configurable event logging, electronic signatures, and secure data export).
Software & Data Management
The Silarex itself functions as a smart analog/digital transducer; full configuration, diagnostics, and calibration management are handled externally via host controller firmware or SIGAS-provided configuration utilities. Raw sensor outputs include compensated concentration values (ppm or vol.%), internal temperature and pressure readings, diagnostic flags (e.g., low-flow alert, optical path obstruction warning), and heater status. All digital communications adhere to open Modbus register maps—enabling interoperability with third-party SCADA platforms (e.g., Ignition, Siemens Desigo, Schneider EcoStruxure). When deployed in GLP/GMP contexts, timestamped concentration records can be archived with traceable metadata—including calibration history, firmware version, and environmental compensation coefficients—ensuring full data integrity and regulatory defensibility.
Applications
- Continuous emission monitoring (CEMS) for boiler flue gas: simultaneous CO₂, CO, NO, and SO₂ tracking per EN 15267 and EPA Method 10
- Biogas quality assurance in anaerobic digestion plants: real-time CO₂/CH₄ ratio estimation and H₂S surrogate monitoring via CO cross-sensitivity profiling
- Indoor air quality (IAQ) management in smart buildings: demand-controlled ventilation based on CO₂ and combustion byproduct thresholds
- Industrial furnace and kiln atmosphere control: closed-loop feedback for stoichiometric combustion optimization
- Hazardous area safety interlocks: rapid CO or SO₂ detection in confined spaces or tunnel ventilation systems
- Research-grade gas mixture analysis in environmental simulation chambers and material outgassing studies
FAQ
What gases does the Silarex detect simultaneously?
The Silarex is configured as a fixed multi-gas module—common variants include CO₂/CO, CO₂/NO/SO₂, or CO₂/CO/NO/SO₂ combinations. Each variant uses dedicated optical filters and detector channels optimized for the target absorption bands.
Does the Silarex require periodic calibration?
While zero calibration is recommended every 3–6 months in critical applications, the dual-beam architecture and thermal stabilization significantly extend calibration intervals compared to single-beam NDIR or electrochemical sensors. Span calibration is typically required only after sensor relocation or exposure to extreme contamination events.
Can the Silarex operate in high-humidity environments?
Yes—its gold-coated chamber and internal temperature control mitigate condensation effects. However, inlet gas must remain non-condensing; an external Peltier cooler or membrane dryer is advised if dew point exceeds 5 °C.
Is the Modbus interface compatible with standard industrial PLCs?
Yes—Modbus ASCII/RTU over TTL-level serial (3.3 V logic) is natively supported by most modern PLCs. An RS-485 converter may be required for longer cable runs or electrically noisy environments.
What is the expected service life under continuous operation?
Based on accelerated lifetime testing and field data, the Silarex maintains metrological performance for ≥5 years (43,800 hours) under nominal conditions (24/7 operation, 25 °C ambient, stable flow), with no scheduled component replacement.
