Detection principle of CO electrochemical sensor of gas detector
The carbon monoxide gas sensor is used in conjunction with the alarm and is the core detection component in the alarm. It is based on the principle of constant potential electrolysis. When carbon monoxide diffuses into the gas sensor, its output terminal generates a current output, which is provided to the sampling circuit in the alarm, playing a role in converting chemical energy into electrical energy. When the gas concentration changes, the output current of the gas sensor also changes proportionally. The intermediate circuit of the alarm converts and amplifies the output to drive different execution devices, completing the detection and alarm functions of sound, light, and electricity. Together with the corresponding control device, it forms an environmental detection or monitoring alarm system.
When carbon monoxide gas diffuses onto the surface of the working electrode through the pores on the outer shell and the breathable membrane, it undergoes oxidation on the working electrode under the catalytic action of the working electrode. The chemical reaction formula is:
CO+H2O → CO2+2H++2e-
The H+ions and electrons generated by the oxidation reaction on the working electrode are transferred to the counter electrode at a certain distance from the working electrode through the electrolyte, and undergo a reduction reaction with oxygen in the water. The chemical reaction formula is:
1/2O2+2H++2e - → H2O
Therefore, a reversible oxidation-reduction reaction occurs inside the sensor. The chemical reaction formula is:
2CO+2O2 → 2CO2
The reversible oxidation-reduction reaction always occurs between the working electrode and the counter electrode, and generates a potential difference between the electrodes.
However, due to the polarization of the electrodes caused by reactions occurring on both electrodes, it is difficult to maintain a constant inter electrode potential, which also limits the detectable range of carbon monoxide concentration.
To maintain a constant inter electrode potential, we added a reference electrode. In a three electrode electrochemical gas sensor, the output terminal reflects the potential change between the reference electrode and the working electrode. Since the reference electrode does not participate in oxidation or reduction reactions, it can maintain a constant potential between the electrodes (i.e. constant potential), and the change in potential is directly related to the change in carbon monoxide concentration. When a gas sensor generates an output current, its magnitude is proportional to the concentration of the gas. By using an external circuit to measure the output current of the sensor through electrode leads, the concentration of carbon monoxide can be detected with a wide linear measurement range. In this way, by connecting an external signal acquisition circuit and corresponding conversion and output circuits to the gas sensor, it is possible to detect and monitor carbon monoxide gas.
