A potentiometric sensor is a type of chemical sensor that may be used to determine the

analytical concentration Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular of a solute in a solution, in terms of amount of substance per unit volume of solut ...

of some components of the analyte gas or solution. These sensors measure the electrical potential of an

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials d ...

when no current is present.

Principle

The signal is measured as the potential difference (voltage) between the working

and the reference electrode. The working electrode's potential must depend on the concentration of the analyte in the gas or solution phase. The reference electrode is needed to provide a defined reference potential.

Classification of sensors

Potentiometric solid state gas sensors have been generally classified into three broad groups. *Type I sensors have an electrolyte containing mobile ions of the chemical species in the gas phase that it is monitoring. The commercial product, YSZ oxygen sensor, is an example of type I. *Type II sensors do not have mobile ions of the chemical species to be sensed, but an ion related to the target gas can diffuse in the solid electrolyte to allow equilibration with the atmosphere. Therefore, type I and type II sensors have the same design with gas electrodes combined with metal and an electrolyte where oxidized or reduced ions can be electrochemically equilibrated through the

electrochemical cell An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic o ...

. In the third type of electrochemical sex , auxiliary phases are added to the electrodes to enhance the selectivity and stability. *Type III sensors make the electrode concept even more confusing. With respect to the design of a solid state sensor, the auxiliary phase looks as part of the electrode. But it cannot be an electrode because auxiliary phase materials are not generally good

electrical conductor In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. Electric current is gene ...

. In spite of this confusion, type III design offers more feasibility in terms of designing various sensors with different auxiliary materials and electrolytes.

References

Sensors Electrochemistry {{analytical-chemistry-stub

Principle

Classification of sensors

See also

References