This blog post explains in detail how a gas leak is detected by an electrical signal through the structure and operating principle of an electrochemical gas sensor.
An electrochemical gas sensor is a device that detects specific gases using electric currents generated by chemical reactions. This sensor detects gas leaks and measures gas concentrations by measuring the amount of electric current generated in the process of the oxidizing and reducing reactions that occur when the gas flows into the sensor and interacts with the electrodes of the sensor.
An electrochemical gas sensor is generally composed of an inlet, a detection part, and a rear part. First, the inlet is responsible for filtering out impurities other than the gas to be detected when gas enters the sensor, and consists of a dust filter, interference gas filter, and separation membrane. When gas leaks into the air and enters the inlet of the sensor, impurities other than gas, such as dust and water, are first filtered out by the dust filter, and only gas is sent to the interference gas filter. After that, the interference gas filter adsorbs gases that interfere with the detection of a specific gas and sends only the gas to be detected to the separation membrane. The separation membrane is a device that separates the inflow and detection sections, and the gas sent from the interference gas filter flows into the detection section through the separation membrane for accurate measurement.
The sensing part is responsible for generating electric current through a redox reaction when gas flows into it, and it consists of a working electrode, counter electrode, and reference electrode. The sensing part has a constant electric current flowing from the reference electrode even in normal times, and the electrodes of the sensing part are immersed in water containing an electrolyte. The electrolyte, when dissolved in water, enables the movement of electrons and acts as a medium to generate electric current. The gas that passes through the separation membrane and reaches the sensing part first undergoes an oxidation reaction that reacts with water at the working electrode to generate hydrogen ions and electrons. To actively induce this oxidation reaction, the working electrode is in the form of a porous membrane with multiple holes, and is coated with a catalyst such as platinum to increase the speed of the oxidation reaction. The hydrogen ions and electrons generated through the oxidation reaction move to the counter electrode through the electrolyte, and at the counter electrode, a reduction reaction occurs in which hydrogen ions and electrons combine with oxygen supplied from the oxygen inlet at the rear to become water. During this process, a current is generated in proportion to the amount of electrons moving between the working electrode and the counter electrode, and the amount of current generated is proportional to the concentration of the gas that has been introduced.
Finally, the rear section is mainly responsible for checking for gas leaks and measuring the concentration of leaked gas through the current generated in the detection unit, and consists of a current collector, sensor pins, and an oxygen inlet. The newly generated current in the detection unit is collected in one place through the current collector and then transferred to the sensor pins. The sensor pin compares the amount of newly generated current with the amount of current that normally flows, and if the amount of newly generated current is greater, it detects a gas leak and measures the gas concentration. At this time, the sensor also goes through a self-calibration process at regular intervals to improve the accuracy of gas concentration measurement. In this process, the status of the reference electrode and the counter electrode inside the sensor is checked, and the electrodes are cleaned or replaced as necessary.
On the other hand, when the gas detected by the gas sensor is above the standard concentration, the alarm connected to the sensor will sound an alarm to notify the user. There are two types of alarms: immediate alarms and delayed alarms. Immediate alarms sound an alarm immediately when the gas concentration exceeds the alarm set value set in the sensor. This type of alarm is mainly used when the occurrence of gas itself is dangerous, such as in the case of toxic gases. The delay alarm type does not immediately sound an alarm even if the detected gas concentration exceeds the alarm setting, but instead sounds an alarm when the gas concentration remains above the alarm setting for a certain period of time set as the delay time. This type of alarm is characterized by not sounding an alarm in the event of a temporary gas leak, such as when a high concentration of gas is detected instantaneously, as in the case of a gas stove ignition malfunction.
In addition, electrochemical gas sensors can be manufactured in various shapes and sizes depending on the type of gas. For example, there are sensors optimized to detect specific gases, such as carbon monoxide (CO) sensors, hydrogen sulfide (H2S) sensors, and ammonia (NH3) sensors, which use different electrode materials and electrolytes to achieve maximum efficiency. In addition, sensors that are miniaturized or enlarged to fit portable devices or industrial facilities have been developed and are being used in various environments.
Electrochemical gas sensors are playing an important role in various fields such as industrial sites, indoor air quality management, and home safety devices due to these advantages. Along with the development of gas sensors, more sophisticated and reliable detection technologies are being developed, and this has enabled us to enjoy a safer and more pleasant living environment.
