Potentiometric sensors detect ionic atoms or molecules in a compound that carry an electrical charge, without requiring a current to flow. The most common use is in oxygen sensors in automobiles, but they are also used in analytical chemistry, industrial processes, and environmental pollution control.
A potentiometric sensor is a type of chemical sensor used in a wide variety of industrial processes to determine the volumetric presence of a compound based on the detection of ionic atoms or molecules in the compound that carry an electrical charge. The sensor does not require a current to flow, merely that the compound itself, liquid or gaseous, pass between the electrodes of the sensor device. One of the most common potentiometric sensor units produced as of 2011 is the oxygen sensor built into automobiles, but there are many other uses for the technology.
The basic function of a potentiometer which is the heart of a potentiometric sensor is that a known voltage on a reference electrode is used as a comparison to a changing voltage on a working electrode. The voltage difference occurs when a solid electrolytic compound between the two electrodes obtains an electric charge when a liquid or gas passes in the form of an ionic conductor. The charge level is used to determine the amount of ions present and this value can then be compared to expected mass values and activate the controls to maintain a desired equilibrium state.
Oxygen sensors, also known as lambda sensors, have been included in US-made automobiles since the 1980s as commonly used potentiometric sensors and are there to ensure vehicles meet pollution control standards in some states such as California and to optimize engine performance for fuel efficiency. They work by measuring the amount of ionized oxygen in an automobile’s exhaust stream while the engine is running. The microprocessors in the vehicle then take this value and compare it with the optimal values for the exhaust gases. If the output changes, the computer control can adjust the vehicle’s air/fuel mixture and ignition timing to ensure more complete combustion of the fuel and reduced pollution. All types of vehicles, whether running on diesel, petrol, ethanol or combinations of these fuels, use these sensors and more modern versions of the devices measure a range of different exhaust gases in addition to just oxygen.
Other uses for a potentiometric sensor include trace gas analysis in analytical chemistry up to parts per trillion and for determining the polar amount of solvents such as water, alcohol and other chemicals used in creating precise industrial solution formulas. Research since 2011 has also led to the use of the potentiometric sensor in pharmaceutical analyses. They are used to detect lead and surfactants in wastewater streams from treatment plants and for many other reasons in the agricultural and medical sectors, as well as for environmental pollution control in a wide variety of industries. Potentiometric ion membrane sensors used to detect heavy metals, such as lead or to determine the pH level of soil samples, can produce results in 15 seconds or less and be used repeatedly for up to four months without degrading.
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