Technical Principle and Core Advantages of Electrochemical Sensors

Electrochemical gas sensors are based on the oxidation or reduction reaction of the target gas at the working electrode, generating a measurable current signal. The reaction typically follows a three-electrode or four-electrode structure design. The Nexisense series adopts a high-stability electrolyte system and noble metal catalytic electrodes, combined with anti-interference filter membranes, to achieve selective response to specific gases.

Typical performance indicators include:

• Linear range: 0-100/500/1000/2000 ppm (depending on gas type)

• Resolution: 0.1-1 ppm

• Response time (T90): ≤30 s

• Expected service life: 3-8 years (under continuous operation)

• Cross-interference: key interfering gases<5-10%

• Operating environment: -20°C to +50°C, 15-90% RH

The four-electrode structure (ME4 series) further improves zero-point stability and resistance to background current through a reference electrode and auxiliary electrode, performing excellently in long-term industrial online monitoring.

Main Target Gases and Typical Application Scenarios

Nexisense electrochemical sensors cover a wide range of common industrial toxic and hazardous gases and are widely used in the following high-risk scenarios.

Petrochemical, Chemical, and Refinery Sites

Focus on monitoring irritating and asphyxiating gases such as H₂S, SO₂, Cl₂, NH₃. Sensors are deployed in fixed multi-point monitoring stations, with 4-20 mA or RS485 outputs connected to distributed control systems (DCS) or safety instrumented systems (SIS), enabling real-time concentration trend analysis, over-limit alarms, and interlock control. In real projects, H₂S sensor arrays combined with wind direction and speed data enable leak source localization and emergency evacuation guidance.

Coal Mines, Tunnels, and Underground Projects

For monitoring needs of CO, CO₂, and H₂S associated with CH₄, Nexisense modules are integrated into intrinsically safe mining instruments or fixed monitoring substations, supporting Modbus RTU protocol and mine ring network communication, ensuring compliance with coal mine safety standards such as AQ 6205.

Sewage Treatment Plants and Municipal Pipe Networks

Sewers, septic tanks, and sludge treatment areas often produce H₂S, NH₃, and small amounts of CH₄. Sensors are installed at pumping stations, manhole sampling points, or mobile inspection equipment, with output signals linked to ventilation systems and personnel-worn alarms, reducing risks in confined space operations.

Environmental Monitoring and Hazardous Waste Treatment

Used for monitoring SO₂, NO₂, Cl₂, PH₃, and other gases in incinerator exhaust, industrial park boundaries, and hazardous chemical warehouses. The modular design facilitates integration into CEMS (Continuous Emission Monitoring Systems) or ambient air quality monitoring stations, complying with relevant standards such as HJ 1012.

Portable and Mobile Detection Equipment

Four-electrode sensors and pre-calibrated modules are widely used in industrial hygiene inspections, multi-gas detectors, and emergency response equipment, providing high repeatability and fast warm-up characteristics.

Selection Guide and System Integration Considerations

When selecting, it is recommended to focus on the following key points:

• Target gas and range matching: H₂S preferably 0-100 ppm, NH₃ 0-100/500 ppm, CO 0-1000 ppm, Cl₂ 0-50 ppm, etc.

• Electrode structure: three-electrode suitable for cost-sensitive projects, four-electrode recommended for high-precision, long-cycle online monitoring.

• Output format: bare sensor, module with amplification circuit (4-20 mA / 0-2 V / UART), digital bus module.

• Environmental adaptability: verify explosion-proof rating (Ex ia IIC T4 Ga / Ex d IIC T6 Gb), poison resistance, and temperature/humidity compensation range.

• Certification and compliance: prioritize products certified by CE, ATEX, IECEx, CMC, CPA, etc.

Integration considerations:

• Installation position should avoid direct airflow impact, strong electromagnetic fields, and sudden high-concentration exposure; sampling heads or explosion-proof enclosures are recommended.

• Signal lines should use shielded cables; 4-20 mA loops are recommended in three-wire configuration to reduce line resistance effects.

• After system power-on, at least 30 minutes of warm-up and zero-point calibration are required; field or laboratory span calibration is recommended every 3-6 months.

• When deploying multi-sensor arrays, pay attention to possible interactions between different gas sensors; add physical isolation or algorithmic compensation if necessary.

• For integration with PLC/SCADA/BMS, signal isolators are recommended to prevent ground loops; Modbus RTU addresses and baud rates need unified planning.

OEM Customization and Bulk Supply Advantages

Nexisense offers OEM/ODM services from individual sensors to complete detection modules, supporting:

• Optimization of electrode formulations for specific gas ranges, sensitivity, and anti-interference characteristics

• Customized dimensions, interface types (M12, aviation plugs, etc.), and communication protocols (Modbus, HART, LoRa, etc.)

• Multi-parameter compensation algorithms for temperature, pressure, and humidity

• Brand labeling, serialization management, and supply chain traceability

Bulk supply capacity covers orders from thousands to hundreds of thousands of units, with stable delivery times, tiered pricing, and joint reliability verification support. Long-term partners can access priority technology iteration channels and sample testing resources.

Frequently Asked Questions (FAQ)

1. 1.What is the main difference in long-term stability between Nexisense four-electrode and three-electrode sensors?
   Four-electrode sensors significantly reduce zero drift and background current effects through an independent reference electrode, suitable for fixed monitoring scenarios with continuous operation exceeding 3 years.

2. 2.How to address the impact of high humidity and sulfide deposition on H₂S sensors in sewage treatment plants?
   Use versions with high-polymer anti-permeation membranes, combined with regular cleaning of sampling heads or purge air paths, typically maintaining service life above 4 years.

3. 3.How to achieve seamless integration of the 4-20 mA output from sensor modules with PLCs of different brands?
   The output is an active two/three-wire signal, with load resistance ≤500 Ω, zero point at 4 mA and full scale at 20 mA; HART-compatible versions allow online parameter reading.

4. 4.How to control cross-interference between different sensors in multi-gas monitoring stations?
   Selective membrane design keeps cross-interference<10%; at the system level, algorithmic compensation or physical delayed sampling can further suppress it.

5. 5.What are the warm-up time requirements for sensors in portable detectors?
   Nexisense modules typically reach ±5% accuracy in<60 s, suitable for quick-start inspections; four-electrode versions offer more stable warm-up.

6. 6.What is the minimum order quantity and cycle time for OEM customization of specific gases (e.g., PH₃ or ETO)?
   Standard gases start at 500-1000 units; special gas formulation development projects typically start at 2000 units, with a development cycle of 8-16 weeks.

7. 7.Is the response performance of sensors reliable in low-temperature environments at -20°C?
   Optional built-in heating compensation circuit extends response time by about 20-30% at -20°C, with linearity maintained within ±10%.

8. 8.How to implement Modbus RTU communication between sensors and SCADA systems?
   Modules support standard Modbus RTU, with selectable addresses 1-247, baud rates 1200-115200 bps, and function codes 03/04 for reading concentration and status registers.

9. 9.Are calibration certificates and consistency reports provided for each batch in bulk supply?
   Yes, factory zero/span calibration data, batch consistency statistics, and optional third-party test reports are provided.

10. 10.What is the recommended sensor placement density and alarm logic for boundary monitoring in hazardous chemical parks?
    It is recommended to place 1-2 monitoring points per 100-300 m², using two-level alarms (warning value at 50% TLV, alarm value at 100% TLV), linked to audible/visual alarms and fan/valve actuators.

Conclusion

Nexisense specializes in providing reliable electrochemical toxic and hazardous gas detection solutions for industrial safety, environmental monitoring, and hazardous chemical enterprises. If your company requires sensor selection, solution design, or customization support for fixed monitoring systems, portable instrument development, OEM integration, or multi-gas projects, feel free to contact us to further discuss specific requirements and collaboration methods. Let’s work together to build a safer industrial gas environment.