Cubic SJH-5B1 Miniature NDIR Methane (CH₄) Gas Sensor
| Brand | Cubic |
|---|---|
| Origin | Hubei, China |
| Manufacturer Type | Authorized Distributor |
| Country of Origin | China |
| Model | SJH-5B1 |
| Price | USD 298 (FOB) |
| Detection Principle | Non-Dispersive Infrared (NDIR) |
| Measured Gas | Methane (CH₄) |
| Range | 0–5% vol |
| Accuracy | ≤±0.06% vol (0–1% vol), ≤±6% of reading (1–5% vol) |
| Resolution | 0.01% vol |
| Operating Temp. | −40°C to +70°C |
| Operating Humidity | 0–95% RH (non-condensing) |
| Storage Temp./Humidity | −40°C to +85°C / 0–95% RH |
| Response Time (T90) | <25 s |
| Lifetime | >10 years |
| Dimensions | Φ20 × 16.6 mm (excluding pins) |
| Output Options | Analog voltage (0–5 V or 0–10 V configurable) and UART digital interface (TTL/RS232) |
| Cross-Sensitivity Mitigation | Immune to ethanol, acetic acid, CO, H₂, and common VOCs |
| Environmental Robustness | Integrated humidity compensation |
Overview
The Cubic SJH-5B1 is a miniature, industrial-grade non-dispersive infrared (NDIR) methane (CH₄) gas sensor engineered for continuous, real-time concentration monitoring in safety-critical and infrastructure environments. Unlike catalytic bead or metal oxide semiconductor (MOS) sensors, the SJH-5B1 employs dual-wavelength NDIR spectroscopy—utilizing a dedicated CH₄ absorption band near 3.3 µm—to deliver inherent selectivity, high signal-to-noise ratio, and immunity to poisoning or drift from ambient contaminants. Its optical architecture features a hermetically sealed measurement chamber with temperature-stabilized IR source and pyroelectric detector, enabling stable performance across wide thermal and hygric gradients. Designed for integration into fixed gas detection systems, portable analyzers, and embedded safety controllers, the SJH-5B1 meets the functional safety expectations of industrial gas monitoring without requiring frequent recalibration or field maintenance.
Key Features
- True NDIR detection principle with optical path optimization for methane-specific absorption at 3.3 µm—eliminating cross-sensitivity to hydrogen, carbon monoxide, ethanol, acetic acid, and hydrocarbons below C₂
- Integrated temperature and humidity compensation algorithms ensuring ±0.06% vol accuracy over 0–1% vol range, validated across −40°C to +70°C and 0–95% RH (non-condensing)
- Low-power operation (<80 mW typical), suitable for battery-powered or energy-constrained deployments in remote or intrinsically safe enclosures
- Dual-output interface: factory-configurable analog voltage output (0–5 V or 0–10 V) and TTL-level UART serial interface (default 9600 bps, ASCII protocol) for seamless PLC, DCS, or microcontroller integration
- Compact cylindrical form factor (Φ20 × 16.6 mm, excluding pins) with gold-plated solder pins—designed for surface-mount or through-hole PCB assembly
- Onboard diagnostics including supply voltage monitoring, internal temperature reporting, and optional high-humidity alarm flag output for predictive system health management
- Support for optional firmware-based auto-zero and span calibration routines—compatible with external reference gas triggers or scheduled internal self-check sequences
Sample Compatibility & Compliance
The SJH-5B1 is optimized for direct sampling of ambient air and process gas streams containing methane in concentrations up to 5% vol. It exhibits no measurable interference from CO₂ (up to 10,000 ppm), water vapor (within specified RH limits), or common background gases encountered in coal mines, utility tunnels, and natural gas distribution facilities. While not certified to ATEX or IECEx as a standalone device, the sensor module complies with RoHS 2011/65/EU and REACH (EC 1907/2006) directives. When integrated into end-user equipment, it supports compliance pathways aligned with EN 50194-1 (gas detectors for domestic use), EN 62061 (functional safety of machinery), and ISO 26304 (performance requirements for fixed CH₄ detectors). Its 10+ year operational lifetime and long-term baseline stability (>2% drift/year under accelerated aging tests) align with IEC 61508 SIL-2 hardware fault tolerance targets for safety-related subsystems.
Software & Data Management
The SJH-5B1 communicates via a documented ASCII command set over UART, enabling host systems to read real-time CH₄ concentration, internal temperature, relative humidity estimate, diagnostic status flags, and firmware version. Optional configuration registers allow setting alarm thresholds, output scaling factors, and communication parameters. For traceable data acquisition in regulated environments (e.g., municipal utility monitoring per EPA Method 21 or ISO 16000-29), users may implement timestamped logging with audit-trail metadata—supporting GLP-aligned record retention when paired with compliant host firmware. The analog output channel maintains monotonic linearity (R² > 0.9998) across full scale, facilitating straightforward integration with legacy 4–20 mA transmitters via external signal conditioning.
Applications
- Fixed-point methane monitoring in underground utility vaults, telecom manholes, and district heating tunnels where explosive atmospheres require Class I, Division 2 hazard mitigation
- OEM integration into portable multi-gas detectors used by fire departments and mine rescue teams—leveraging low power draw and rapid T90 response for emergency situational awareness
- Smart gas metering and leak detection modules in residential/commercial natural gas regulators and pressure-reducing stations
- Environmental monitoring nodes deployed along landfill perimeter fences or biogas collection ducts—operating reliably under diurnal thermal cycling and high ambient humidity
- Research-grade validation sensors in laboratory test benches evaluating catalytic oxidation efficiency or membrane separation performance for CH₄ recovery
FAQ
Does the SJH-5B1 require periodic zero calibration in the field?
No—its NDIR optical design provides inherent zero stability. However, optional auto-zero routines are supported via host-triggered commands if environmental contamination or long-term optical window soiling is anticipated.
Can the sensor operate continuously at 95% RH without condensation risk?
Yes, provided ambient conditions remain non-condensing. The housing incorporates hydrophobic vent membranes and internal humidity compensation to maintain accuracy up to 95% RH at 40°C.
Is the UART interface compatible with Modbus RTU or other industrial protocols?
No—the native interface uses a proprietary ASCII protocol. Protocol translation to Modbus RTU or BACnet MS/TP requires an external gateway or host-side software abstraction layer.
What is the recommended warm-up time before achieving full accuracy?
Less than 60 seconds after power-on at 25°C ambient. Full thermal stabilization across extreme temperatures (−40°C/+70°C) may require up to 5 minutes.
Does Cubic provide calibration certificates traceable to NIST standards?
Yes—factory calibration reports (with uncertainty budgets) are available upon request and include traceability to national metrology institutes via accredited third-party labs (ISO/IEC 17025).
