Electrochemical Gas Sensors: Principles, Working Mechanism, and Key Characteristics
- Nguyen Vinh Loc
- 1 day ago
- 10 min read
Updated: 1 hour ago
Electrochemical gas sensors play a critical role in modern gas detection systems, particularly in applications where accuracy and selectivity are essential. They are widely used across industrial safety, environmental monitoring, and confined-space protection to detect toxic gases and oxygen levels at low concentration ranges.
But what exactly is an electrochemical gas sensor, and how does it work? Unlike metal oxide or catalytic gas sensors, electrochemical gas sensors rely on electrochemical reactions to generate an electrical signal that is directly proportional to gas concentration. This operating principle enables reliable and repeatable measurements in safety-critical environments.
This article provides a clear, system-level explanation of electrochemical gas sensors, covering their working mechanism, circuit considerations, advantages and limitations, andtypical industrial applications. It also examines how electrochemical sensing technology is evolving when integrated into wireless gas monitoring systems and Industrial IoT architectures.
What Is an Electrochemical Gas Sensor?
An electrochemical gas sensor is a gas-sensing device that detects the concentration of a specific target gas by converting a chemical reaction into an electrical signal. The sensor operates by allowing the target gas to interact with electrodes inside an electrochemical cell, where a controlled oxidation or reduction reaction occurs.
The electrical current generated by this reaction is directly proportional to the gas concentration, enabling precise measurement even at very low ppm levels. This characteristic makes electrochemical gas sensors particularly suitable for applications where accuracy and reliability are critical, such as industrial safety and environmental monitoring.
Unlike metal oxide semiconductor (MOS) or catalytic bead sensors, electrochemical gas sensors do not require a heating element. As a result, they typically consume less power and exhibit better selectivity toward specific gases. Electrochemical gas sensors are commonly recognized for the following characteristics:
High sensitivity to target gases at low concentration ranges
Strong selectivity based on electrode chemistry
Linear output signal over the specified measurement range
Low power consumption, suitable for battery-powered systems
Because of these properties, electrochemical gas sensors are widely used for detecting toxic gases such as carbon monoxide (CO), hydrogen sulfide (H₂S), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), as well as for monitoring oxygen (O₂) levels.
Electrochemical Gas Sensor Working Principle
The working principle of an electrochemical gas sensor is based on controlled electrochemical reactions that occur when a target gas interacts with electrodes inside the sensor cell. Each sensor is designed so that only specific gases participate in these reactions, ensuring selective and repeatable measurements.
A typical electrochemical gas sensor consists of three main components:
Working electrode (WE) – the surface where the target gas undergoes oxidation or reduction
Counter electrode (CE) – completes the electrical circuit by balancing the electrochemical reaction
Reference electrode (RE) – maintains a stable electrode potential to ensure measurement accuracy
These electrodes are immersed in an electrolyte that enables ion transport between them.
The sensing process follows a controlled sequence:
The target gas diffuses through a porous membrane into the sensor cell.
At the working electrode, the gas participates in an electrochemical reaction.
This reaction releases or consumes electrons, generating an electrical current.
The current flows between the working and counter electrodes.
The measured current is proportional to the gas concentration.
Because the reaction rate depends on the amount of gas present, the sensor output provides a linear and reliable indication of concentration within its specified range.
Selectivity in electrochemical gas sensors is achieved through electrode material and catalyst design. By choosing appropriate electrode compositions, manufacturers can tailor sensors to respond primarily to a specific gas while minimizing interference from others. This chemical selectivity is one of the key reasons electrochemical gas sensors are widely used in applications where false alarms or cross-sensitivity could create safety risks.
At its core, the principle of an electrochemical gas sensor is straightforward. When a target gas enters the sensor, it triggers a controlled chemical reaction at the electrode surface. This reaction produces an electrical current, which serves as the sensor’s output signal. The key idea is that the rate of the electrochemical reaction depends on the amount of gas present. As gas concentration increases, more reaction occurs, generating a higher current. When gas concentration decreases, the reaction rate and output current decrease accordingly. Because this current is directly related to gas concentration, electrochemical gas sensors can provide linear, stable, and repeatable measurements without complex signal interpretation. This simplicity at the sensing level is what makes electrochemical gas sensors highly reliable for safety and monitoring applications.
Electrochemical Gas Sensor Circuit – Functional Overview
An electrochemical gas sensor does not produce a voltage signal directly. Instead, it generates a very small electrical current as a result of the electrochemical reaction inside the sensor cell. The primary role of the sensor circuit is to convert this current into a usable voltage signal and ensure measurement stability under real-world conditions.
Core function of the sensor circuit
At a functional level, the circuit must perform three key tasks:
Convert low-level sensor current into a measurable voltage
Maintain stable electrode potentials for accurate sensing
Condition the signal for further digital processing
Because the output current is often in the nanoampere to microampere range, circuit design plays a critical role in overall sensor performance.
Transimpedance amplifier (TIA)
The most important circuit element in an electrochemical gas sensor system is the transimpedance amplifier (TIA). The TIA converts the sensor’s output current into a proportional voltage by passing the current through a precision feedback resistor. This approach offers several advantages:
High sensitivity to very small currents
Linear voltage output proportional to gas concentration
Low noise when properly designed
The quality of the TIA directly affects accuracy, resolution, and long-term stability.
Role of the reference electrode in circuit design
In three-electrode electrochemical gas sensors, the reference electrode is used to control the potential of the working electrode. The circuit actively maintains this potential using feedback control, ensuring that the electrochemical reaction occurs under consistent conditions. This electrode potential control is essential for:
Reducing measurement drift
Improving repeatability
Minimizing the influence of environmental changes
Signal conditioning and digital processing
After current-to-voltage conversion, the signal typically passes through:
Filtering stages to reduce electrical noise
Amplification or scaling circuits
An analog-to-digital converter (ADC) for digital processing
Once digitized, the signal can be compensated for temperature effects, calibrated, and transmitted to monitoring systems.
System-level implications
While electrochemical gas sensors are often evaluated based on their sensing element alone, system-level performance depends heavily on circuit design. Poor electronics can degrade accuracy, increase noise, or shorten effective sensor lifetime—even if the sensing element itself is high quality. This is why modern gas detection solutions increasingly consider the sensor, electronics, and communication layer as a single integrated system rather than separate components.
Types of Electrochemical Gas Sensors
Electrochemical gas sensors can be classified based on their internal structure and electrolyte design. Understanding these distinctions helps engineers and system integrators select suitable sensor technologies for specific environments and deployment models.
Two-electrode vs three-electrode sensors
Early electrochemical gas sensors were commonly built using a two-electrode configuration consisting of a working electrode and a counter electrode. While simple and cost-effective, this design is more vulnerable to drift and environmental influences.
Most modern industrial gas detection systems rely on three-electrode electrochemical sensors, which add a reference electrode to stabilize the working electrode potential. This configuration improves measurement accuracy, repeatability, and long-term stability, making it the preferred choice for safety-critical applications.
Liquid electrolyte electrochemical sensors
The majority of electrochemical gas sensors used in industrial safety today are based on liquid electrolyte technology. In these sensors, the electrolyte enables ion transport between electrodes, allowing controlled oxidation or reduction reactions to occur when the target gas is present. Liquid electrolyte electrochemical sensors are widely adopted due to their:
High sensitivity at low ppm concentrations
Strong selectivity for specific target gases
Proven performance across a broad range of toxic and oxygen-sensing applications
However, their operational lifetime can be influenced by environmental conditions such as temperature extremes, mechanical stress, or gradual electrolyte depletion.
Solid-state electrochemical gas sensors
Solid-state electrochemical gas sensors replace liquid electrolytes with solid or polymer-based materials. This approach reduces leakage risk and can improve resistance to vibration and orientation changes.
Despite these advantages, solid-state electrochemical sensors remain less common in mainstream industrial safety systems due to higher cost and more limited availability across gas types compared to liquid-electrolyte designs.
Advantages and Disadvantages of Electrochemical Gas Sensors
Electrochemical gas sensors are widely used in industrial safety and monitoring applications because they offer a strong balance between sensitivity, selectivity, and power efficiency. However, like any sensing technology, they also present certain limitations that must be considered during system design and deployment.
One of the main advantages of electrochemical gas sensors is their ability to detect gases accurately at low concentration levels. The electrochemical reaction produces a linear output signal, which simplifies calibration and signal interpretation.
Electrochemical gas sensors typically offer high selectivity for specific target gases due to tailored electrode materials and catalysts. This reduces the likelihood of false alarms in environments where multiple gases may be present.
Another key advantage is low power consumption. Because these sensors do not require a heating element, they are well suited for battery-powered and wireless gas monitoring systems.
Despite their strengths, electrochemical gas sensors have a finite operational lifetime. Over time, electrolyte depletion and electrode aging can reduce sensor sensitivity, requiring periodic replacement or recalibration.
Electrochemical sensors may also exhibit cross-sensitivity to certain gases, particularly in complex industrial environments. Temperature and humidity variations can further influence sensor output if not properly compensated at the system level.
Additionally, electrochemical gas sensors are typically designed for specific target gases and measurement ranges, limiting their flexibility compared to some multi-gas sensing technologies.
Typical Applications of Electrochemical Gas Sensors
Electrochemical gas sensors are widely deployed in environments where accurate detection of toxic or oxygen-related gases is essential for safety, regulatory compliance, and operational continuity. Their sensitivity, selectivity, and low power consumption make them suitable for both fixed and distributed monitoring systems.
Industrial safety and worker protection
One of the most common applications of electrochemical gas sensors is industrial safety monitoring. Facilities such as manufacturing plants, chemical processing sites, and refineries rely on these sensors to detect hazardous gases like carbon monoxide (CO), hydrogen sulfide (H₂S), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂).
Early detection helps prevent acute exposure, supports alarm systems, and enables rapid response before gas concentrations reach dangerous levels.
SO₂ Detection in Industrial Safety
This monitoring function can be achieved using Daviteq’s LoRaWAN Ex d battery-powered electrochemical gas sensor, which enables wireless, low-power detection of toxic gases such as SO₂ in hazardous industrial environments.
Confined space monitoring
Electrochemical gas sensors are frequently used in confined spaces, including tunnels, storage tanks, pipelines, and underground facilities. In these environments, oxygen depletion or the buildup of toxic gases can occur rapidly and without warning.
Because electrochemical sensors provide reliable low-ppm measurements and stable output, they are well suited for continuous monitoring in confined or poorly ventilated areas.
CO Monitoring in Confined Spaces
This use case can be implemented with Daviteq’s LoRaWAN Ex d battery-powered electrochemical gas sensor, supporting wireless and low-power detection of gases such as CO in confined and hazardous spaces.
Oil and gas facilities
In upstream, midstream, and downstream oil and gas operations, electrochemical gas sensors play a critical role in detecting toxic gases and monitoring oxygen levels around equipment, processing units, and maintenance areas.
Their ability to operate without a heating element makes them safer for use in potentially explosive atmospheres when properly certified and integrated into compliant systems.
H₂S monitoring in Oil & Gas Facilities
This monitoring scenario can be supported by Daviteq’s LoRaWAN Ex d battery-powered electrochemical gas sensor, enabling wireless and low-power detection of hazardous gases such as H₂S in oil and gas facilities.
From Standalone Sensors to Wireless Gas Monitoring Systems
Traditional electrochemical gas sensors are often deployed as standalone or wired devices, typically connected to local alarms or centralized control panels. While this approach has been effective for decades, it introduces several limitations when systems need to scale, adapt to changing layouts, or operate in hard-to-reach environments.
Limitations of wired gas detection systems
Wired gas monitoring systems require fixed infrastructure, including power supply and communication cabling. In industrial environments, this can lead to:
High installation and commissioning costs
Limited flexibility when equipment layouts change
Challenges in monitoring remote or hazardous locations
Maintenance and system expansion can also become complex, especially in facilities with distributed assets or multiple monitoring zones.
Wireless electrochemical gas monitoring systems
Wireless gas monitoring systems extend traditional electrochemical sensing by integrating low-power electronics and wireless communication into the sensor platform. Instead of relying on fixed wiring, sensor data is transmitted to a central monitoring system over long-range wireless networks.
When combined with electrochemical sensing technology, wireless systems enable:
Rapid deployment without cabling
Continuous monitoring in hazardous or inaccessible areas
Battery-powered operation with multi-year lifetime
Centralized data visibility across multiple sites
Wireless technologies such as LoRaWAN, NB-IoT, and LTE-M are commonly used to support reliable, long-distance communication while maintaining low power consumption.
System-level considerations
In wireless gas monitoring, overall performance depends not only on the electrochemical sensing element, but also on system-level design. Key considerations include:
Power management and battery life
Environmental protection (enclosure, ingress rating, hazardous-area certification)
Data reliability and network coverage
Integration with monitoring platforms and alarms
A well-designed wireless system preserves the accuracy of the electrochemical sensor while extending its usability across larger and more complex environments.
Electrochemical gas sensors remain a core technology for detecting toxic gases and monitoring oxygen levels in safety-critical environments. Their high sensitivity at low concentrations, strong selectivity, and low power requirements make them a reliable choice across a wide range of industrial and environmental applications.
When selecting electrochemical gas sensors, it is important to consider not only the sensing element itself, but also the broader deployment context. Key factors include the target gas type, required detection range, operating environment, and expected sensor lifetime. Environmental conditions such as temperature, humidity, and potential cross-interference should be evaluated early in the design process.
At the system level, installation constraints, maintenance access, and data availability play an increasingly important role. In many modern deployments, wireless architectures offer greater flexibility by reducing infrastructure requirements while enabling continuous, distributed monitoring across multiple locations.
Ultimately, effective gas detection depends on aligning electrochemical sensing technology with appropriate system design and deployment strategy. By understanding both the capabilities and limitations of electrochemical gas sensors, organizations can implement monitoring solutions that improve safety, reliability, and operational efficiency over the long term.
Comments