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Nexisense MOS Semiconductor Gas Sensor: High-Reliability Integration Solution
Metal oxide semiconductor (MOS) gas sensors, with their significant resistance response to reducing and oxidizing gases, have become core components in industrial process control, environmental monitoring, and safety instrumentation fields. At operating temperatures of 200~400℃, oxygen adsorption on the sensitive material surface forms a depletion layer and barrier; when target gas undergoes redox reaction, barrier height changes lead to significant adjustment in carrier concentration, enabling ppm-level concentration detection.
The Nexisense series sensors combine thick-film multilayer printing and MEMS micro-hotplate processes to achieve miniaturization, power optimization, and batch consistency, successfully applied in fixed gas detectors, portable multi-gas instruments, and air quality monitoring systems.
MOS Gas Sensor Working Principle and Process Evolution
In clean air, oxygen molecules capture conduction band electrons from n-type semiconductors such as SnO₂, WO₃, ZnO, forming O⁻/O₂⁻ ions, establishing space charge layer at surface and grain boundaries, increasing barrier height and resulting in high-resistance state. Reducing gases (e.g., CO, CH₄, C₂H₅OH) react with adsorbed oxygen to release electrons, lowering barrier and decreasing resistance; oxidizing gases (e.g., NO₂, O₃) capture electrons, raising barrier and further increasing resistance.
Process evolution path:
Early thick-film screen printing: heating layer and gas-sensitive layer separated on both sides of Al₂O₃ ceramic substrate, achieving planar structure
Modern MEMS process: silicon-based suspended micro-hotplate significantly reduces thermal mass, heating power reduced to<100mW, response time shortened to <10s
Current integration trend: chip-level packaging, supporting digital output, temperature/humidity compensation, and array design
Nexisense modules typically control heating power at 80~150mW, suitable for battery-powered scenarios or long-term continuous monitoring.
Main Application Scenarios and Project Integration Cases
Industrial Safety and Leakage Monitoring
High-risk sites such as petrochemical, metallurgy, and wastewater treatment plants widely use Nexisense MOS sensors to build fixed combustible/toxic gas detectors, supporting ranges of 0~100%LEL or 0~2000ppm. Module resistance/voltage signals are linearized by MCU and connected to DCS/SCADA for over-limit alarming and valve/ventilation linkage.
Case: Upgrade project in storage tank area of an East China refining enterprise, Nexisense thick-film series sensors deployed in distributed monitoring network, accessed to safety instrumented system (SIS) via RS485 Modbus RTU, effectively monitoring H₂S, NH₃, VOC leaks with response time<15s, system passed SIL2 functional safety assessment.
Ambient Air Quality and Indoor Monitoring
Smart environmental monitoring stations and fresh air systems require multi-component detection of CO, TVOC, ethanol, etc. Nexisense MEMS low-power modules are integrated into sensor arrays, using different doped materials to improve selectivity, supporting composite detection schemes.
Practical application: In Yangtze River Delta industrial park micro-station project, Nexisense sensors combined with electrochemical/NDIR modules achieve continuous monitoring of CO 0~50ppm, TVOC 0~10ppm, data uploaded to environmental platform in real time, compliant with HJ 1012-2018 standard requirements.
Portable and Personal Protective Equipment
Handheld detectors emphasize small size, fast startup, and high reliability. Nexisense planar/MEMS sensors use TO-5/TO-39 metal packaging, resistant to vibration and impact, suitable for emergency rescue and occupational health inspection.
Project: In bulk deployment of portable multi-gas instruments in mining and fire departments, Nexisense modules achieve CH₄/CO/H₂S three-in-one detection, preheating<30s, continuous="" operation="">12h, improving on-site response capability.
Selection Guide and System Integration Considerations
Key selection parameters:
Target gas and range: combustible gas (0~100%LEL), CO (0~1000ppm), TVOC (0~20ppm), NH₃/H₂S (0~100ppm)
Heating voltage/power: 3.0~5.0V DC, 80~200mW
Output form: analog resistance (kΩ~MΩ), voltage divider, I²C/UART digital (optional)
Operating temperature: -20~50℃ (ambient), 200~400℃ (sensitive layer)
Response/recovery time: T90<30s (typical)
Lifetime: >5 years (under continuous heating)
Integration considerations:
Heating control: prefer constant current/constant voltage drive, recommend PWM power modulation to reduce average power consumption.
Circuit design: gas-sensitive resistance voltage divider acquisition, recommend ≥10-bit ADC; digital modules include built-in linearization algorithm.
Environmental compensation: pair with temperature/humidity sensor for baseline drift correction, avoid long-term exposure to high-concentration interference.
Installation position: away from heat sources and strong convection, upstream install dust/waterproof breathable membrane (IP54 or above optional).
EMC protection: use shielded enclosure and power filtering, compliant with GB/T 18268 industrial EMC standard.
Calibration cycle: zero/span calibration with standard gas every 3~6 months, support automatic background air tracking.
Software support: provide SDK, Modbus register table, and reference driver code.
Nexisense OEM/Customization and Bulk Supply Advantages
Nexisense focuses on MOS gas-sensitive technology and provides comprehensive B2B cooperation:
Custom sensitive material formulation and doping to improve selectivity for specific gases (e.g., ethanol, formaldehyde).
Flexible interfaces: analog/digital output, custom protocols, packaging forms (metal can, SMD, module board).
Bulk production: stable monthly capacity, independent control of thick-film/MEMS production lines, reliable delivery.
Technical support: complete characteristic curves, accelerated life test reports, joint reliability verification.
Lifecycle management: 5~8 year supply commitment, EOL advance notice and migration plan.
These services help equipment manufacturers optimize performance, control costs, and accelerate product iteration.
Frequently Asked Questions (FAQ)
What are the main differences between MOS semiconductor sensors and electrochemical/catalytic combustion sensors?
MOS provides broad-spectrum response to reducing gases, long lifetime, no consumable parts, but selectivity depends on material optimization or array; electrochemical has high specificity but limited lifetime, catalytic combustion suitable for combustible gases and requires oxygen participation.How to reduce preheating time and power consumption of MEMS MOS sensors?
Utilizing suspended micro-hotplate + pulse heating, preheating can be shortened to<20s, average power consumption <50mW; Nexisense modules include built-in intelligent heating algorithm.Will the sensor exhibit baseline drift in high-humidity environments?
High humidity affects adsorption equilibrium causing short-term drift; Nexisense integrates humidity compensation and periodic cleaning heating, drift <±10% within RH 20~95%.How to integrate digital output modules with existing monitoring systems?
Supports I²C (400kHz) or RS485 Modbus RTU (9600~115200bps), provides register table and CRC check, compatible with PLC, MCU, and IoT gateways.How to improve selectivity for specific industrial gases (e.g., H₂S or NH₃)?
Through noble metal doping, composite oxides or filter layers, Nexisense can customize sensitive layer, reducing cross-sensitivity to<20%.How to effectively manage zero drift during long-term operation?
Supports automatic background air tracking, weekly cleaning heating cycle; recommend quarterly standard gas verification, built-in drift compensation coefficient.Does OEM customization support multi-gas array integration?
Supports 2~4 channel arrays with differentiated materials per channel, enabling multi-component detection and pattern recognition, improving system intelligence.Does sensor application in explosion-proof areas comply with relevant standards?
Industrial-grade series provides Ex ia IIC T4 Ga intrinsic safety certification, suitable for Zone 0/1; metal packaging enhances protection, meeting GB 3836 series requirements.
Conclusion
Nexisense is committed to continuous iteration of MOS semiconductor gas sensing technology, assisting system integrators and instrument manufacturers in building reliable, cost-effective gas detection solutions. We welcome gas detection equipment manufacturers, safety instrumentation integrators, and environmental monitoring project parties to contact us for detailed specifications, sample evaluation, or customized development discussions, to jointly promote technological progress in industrial safety and environmental monitoring fields.
