Originally posted on https://www.analyticaltechnology.com/analyticaltechnology/gas-water-monitors/blog.aspx?ID=1327&Title=How%20Do%20Electrochemical%20Sensors%20Work?


You probably don’t think about them often, or even know what they’re called—but they can save your life.

We’re talking about electrochemical sensors, aka toxic gas sensors. These are the very devices that monitor your homes for toxic gas that can potentially poison you and your family.

In this article, we’ll explain what they do and how they work. Just in case you were wondering about one of the many things keeping you safe while you sleep.

What do Electrochemical Sensors Do?

Electrochemical sensors are used for detecting oxygen and toxic gases. More specifically, they measure the concentration of a specific gas within an external circuit. This is done by method of oxidation or reduction reactions.

These reactions generate the positive or negative current flow through said external circuit. An electrochemical sensor is made up of a “working” electrode, a “counter” electrode, and usually a “reference” electrode. All of these components sit inside of a sensor housing along with a liquid electrolyte.

At the top of the housing, there is a mechanism made up of a membrane and a diffusion limiting outlet. This outlet allows the outside air to interact with the liquid electrolyte.

A few examples of electrochemical sensors are:

  • Breathalyzer
  • Blood Glucose sensor
  • Respiratory Carbon Dioxide sensor
  • (Electrochemical) Carbon Monoxide sensor
  • (Electrochemical) Oxygen sensor

They’re much more common than the average person knows, which is surprising because they’re typically used to save lives.

How do Electrochemical Sensors Work?

To put things simply, this sensor type works by means of gas diffusion. Gas finds its way into the outlet of the membrane on top of the sensor housing. Once the gas reaches the working electrode, an electrochemical reaction occurs.

This reaction is either an oxidation or a reduction, depending on the type of gas. (For example, carbon monoxide gets oxidized into carbon dioxide, and oxygen gets reduced to water).

Oxidation causes the flow of electrons to move from the working electrode to the counter electrode through the external circuit. Reduction adversely causes the flow of electrons to move from the counter electrode to the working electrode. Either direction of electron flow creates an electric current proportional to the concentration of gas.

The electrons within the external circuit detect and amplify this current. It then scales the output accordingly with the calibration to give a reading in engineered units. The engineered units are read in PPM (parts per million) to give a percentage of the volume of gas.

Electrochemical sensors depend on chemical processes with proportional temperature rates. Since temperatures vary, some form of temperature compensation is encouraged for the most accurate readings.

Now You Know

There are a number of different electrochemical sensors available to measure the air you and your family breathes. Now you have an idea of the very mechanism which monitors your air for high volumes of poison. Without it, you’d have no idea what you’re breathing in.

For information about the different kinds of electrochemical sensors available or general questions, we’re here to help.