Electrochemical Sensors.

Electrochemical Sensors

Principle of operation.  

• Electrochemical sensors work by reacting with the gas of interest and producing an electric signal proportional to the gas concentration.

• The gas first passes through the capillary diffusion barrier and diffuses through the hydrophobic membrane.This allows specific amount of gas  to react with the sensing electrode to produce sufficient amount of electrical signal and also preventing the leak of electrolyte.

• The gas that passes through the barrier reacts at the surface of the sensing electrode involving either an oxidation or reduction reaction.

• A current is generated in the process hence it is called as amperometric gas sensor or a microfuel cell.

Electrochemical Sensor

Importance of Reference Electrode

• For a sensor requiring  an    electrical driving voltage it is important to have a stable & constant potential at the sensing electrode. In reality the potential at the sensing electrode does not remain constant due to continuous chemical reaction . It causes deterioration of the electrodes over the extended periods of time. To improve the performance of the sensor reference electrode is introduced. This reference electrode is placed in close proximity of the sensing electrode. This reference electrode maintains the value of fixed voltage at the sensing electrode.

• No current flows through the reference electrode.

• Current flows between sensing electrode and  counter electrode.