In daily life, we all come into contact with sensors and are aware of the applications of sensors based on different media and principles. Today, let's learn about carbon monoxide sensors and explore how they work.
Carbon monoxide sensors are used in conjunction with alarm devices, so sensors have become an indispensable core component of alarm devices. Their basic principle is based on potentiostatic electrolysis. When external carbon monoxide diffuses and reaches the gas sensor, the output terminal of the sensor will respond and generate a current output, then transmit the acquired information to the alarm device. The sampling circuit in the alarm device converts chemical energy into electrical energy.
If the concentration of external carbon monoxide increases, the output current of the gas sensor will increase accordingly—there is a proportional relationship between the two. When the change in current passes through the alarm device, the current is amplified. After amplification, it can drive various components to achieve the alarm function.
When carbon monoxide is present in the environment, the carbon monoxide gas diffuses and reaches the surface of the sensor's functional electrode through the air holes on the sensor housing. Subsequently, a corresponding chemical reaction occurs at the working electrode—carbon monoxide gas undergoes an oxidation reaction here. Specifically, carbon monoxide reacts with water to form carbon dioxide and two hydrogen ions.
After the oxidation reaction at the working electrode, the hydrogen ions and electrons generated in the reaction are transferred under the action of the electrolyte to the counter electrode of the working electrode. There, they undergo a reduction reaction with oxygen in water, forming water again. In essence, a reversible redox reaction occurs inside the sensor: carbon monoxide reacts with oxygen to produce carbon dioxide.
In other words, this reversible redox reaction takes place continuously, creating a certain potential difference between the two electrodes. However, there is a drawback: the chemical reactions occurring at both electrodes cause electrode polarization. This polarization makes it impossible to measure the potential between the electrodes, which poses significant difficulties for us to detect the concentration of carbon monoxide.
To address this, we need to find a way to keep the potential between the electrodes constant—and this is where a reference electrode is introduced. With the reference electrode, the sensor now involves a three-electrode chemical reaction system. Importantly, the reference electrode does not participate in oxidation or reduction reactions, thereby effectively maintaining a constant potential between the working electrode and the counter electrode.
After this introduction, I believe you have gained a basic understanding of how carbon monoxide sensors work. In fact, if you break it down, their working principle is quite straightforward.
