The electrochemical gas sensor is a commonly used gas sensor that can detect various gases, including:
The electrochemical gas sensor is based on the electrochemical properties of the target substance and converts the chemical quantity of the target substance into an electrical quantity for sensing and detection. It works by reacting with the measured gas and generating an electric signal proportional to the gas concentration.
Most electrochemical gas sensors are current sensors that generate a linearly proportional electric current to the gas concentration.
Figure: Electrochemical cell in the presence of air and CO atmosphere
Figure: Components of an Electrochemical Gas Sensor
An electrochemical gas sensor works by reacting with the gas being measured and producing an electrical signal proportional to the gas concentration.
A typical electrochemical sensor consists of a sensing electrode and a counter electrode, separated by a thin electrolyte layer. Using tiny capillary openings and hydrophobic barrier layers, an appropriate amount of gas can react with the sensing electrode to form a sufficient electrical signal while preventing electrolyte leakage. The gas concentration is determined by measuring the current proportional to the concentration of the gas being measured.
To improve the performance of the sensor, a reference electrode is introduced to maintain a fixed voltage value on the sensing electrode.
Gas molecules react with the sensing electrode while measuring the counter electrode, and the measurement results are usually directly related to the gas concentration.
Figure: The Measurement Method of Electrochemical Gas Sensor
Different gas sensors have their own range, as low as 1ppm and as high as 100%vol. A 1ppm range sensor is used to measure highly toxic gases, while a 100%vol range sensor is used to measure high-concentration oxygen.
The decline in air quality caused by industrialization poses a threat to the quality of life, with the main air pollutants being nitrogen oxides, sulfur oxides, hydrogen sulfide, and some volatile organic compounds. Electrochemical gas sensors are now becoming an essential tool for monitoring and controlling pollutants that affect air quality. They provide a cheaper alternative for widespread air monitoring compared to traditional and more expensive air quality monitoring instruments based on infrared spectroscopy and gas chromatography.
In hazardous areas within the manufacturing and chemical industries, explosion prevention is receiving increasing attention due to the presence of toxic and flammable gases. Monitoring these hazardous areas helps to achieve a safer working environment. Government and industry regulations, such as COSHH and OSHA, require workers to limit exposure to toxic gases and fumes. This has led to an increase in the use of electrochemical gas sensors, which offer better sensitivity and selectivity for a wide range of toxic gases.
Electrochemical oxygen sensors are used in many brands and models of medical respirators and ventilators for respiratory therapy, life support systems, and emergency medicine.
When critically ill patients may not be able to get enough oxygen from the surrounding air due to respiratory problems, ventilators provide a mixture of medical-grade oxygen-rich air from pressurized tanks and the surrounding air.
The percentage of oxygen required depends on the severity of the patient's condition, so measuring the concentration and flow of oxygen is critical to the patient's health.
The small size, ease of implementation, and simple operation of electrochemical sensors make them ideal detection and monitoring devices in the healthcare field.
Figure: Electrochemical Sensors for Healthcare
The use of electrochemical sensors in food industry applications is increasing. Carbon dioxide and ethanol are used in the food and beverage industry, so continuous gas detection is needed to prevent people from ingesting toxic or harmful gases.
Other applications that require gas detection include steam processes, inert gases for packaging, carbonated gases, toxic gases for sterilization, and ammonia for refrigeration.
Figure: Electrochemical Sensors for Food quality control
Electrochemical gas sensors represent a burgeoning class of sensor products that boast a trifecta of desirable traits: compact dimensions, heightened sensitivity, and effortless assembly. This makes them a highly valuable asset in a diverse range of fields, including but not limited to agriculture, environmental monitoring, and healthcare. These sensors are capable of detecting an array of gases, encompassing both inorganic toxic gases and combustible gases. They possess commendable reproducibility and accuracy, linear output, low power consumption, and excellent resolution, among other advantages.
However, it must be noted that electrochemical sensors are incapable of qualitatively analyzing unknown gases, and they possess a finite lifespan. Exposure to concentrations exceeding their operational parameters may result in sensor failure, necessitating careful storage and handling.
As sensor technology continues to advance, electrochemical sensors will undoubtedly proliferate and find their way into practical applications, particularly in the realm of IoT construction where they can demonstrate their full worth.