The pros and cons of electrochemical sensors

What are the advantages and disadvantages of electrochemical sensors?

Responding is Mark Baldigowski, training specialist, Industrial Scientific Corp., Oakdale, PA.

Electrochemical sensing technology began in the early 1950s. Today, it remains the most popular sensing method for detecting oxygen and toxic gases such as carbon monoxide and hydrogen sulfide. This method is not used for measuring combustible gases, but it is the best all-around choice for ambient toxic gas monitoring.

Electrochemical sensors operate by reacting with the gas of interest to produce an electrical signal proportional to that gas concentration. Using electrochemical sensors in your gas detection, similar to any technology, has advantages and disadvantages. It is important that the application information be reviewed before deciding on the technology best suited to your application.

Advantages of electrochemical sensors include:

• Can be specific to a particular gas or vapor in the parts-per-million range. The degree of selectivity depends on the type of sensor, the target gas and the concentration of gas the sensor is designed to detect.
• Linear output, low power requirements and good resolution.
• Excellent repeatability and accuracy. Once calibrated to a known concentration, the sensor will provide an accurate reading to a target gas that is repeatable.
• Does not get poisoned by other gases. The presence of other ambient vapors will not shorten or curtail the life of the sensor.
• Less expensive than most other gas detection technologies. Unlike infrared and PID technologies, electrochemical sensors are economical.

Disadvantages of electrochemical sensors include:

• Narrow or limited temperature range. They are sensitive to temperature and, therefore, the sensors typically are internally temperature compensated. It is better to keep the sample temperature as stable as possible.
• Short or limited shelf life. An electrochemical sensor usually has a shelf life of six months to one year, depending on the gas to be detected and the environment in which it is used.
• Cross-sensitivity of other gases. While this is an advantage, it also can be a disadvantage. Some sensors are subject to interference from other gases. It is important to know what gases may cause interference with your sensor so you are aware of potential false readings.
• The greater the exposure to the target gas, the shorter the life span. Generally, a one- to three-year life expectancy is specified. Low humidity and high temperatures can cause the sensors’ electrolyte to dry out. Exposure to target gas or cross-sensitivity gases also depletes the electrolyte.

Electrochemical sensors are a proven technology that have been used for many years, and will continue to be the cornerstone of gas detection sensors. The convenience of small and hearty sensors always will be of use for personal gas detection devices. But when using them in your gas detection equipment within a specific application, always remember the sensors’ limitations.

Editor's Note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.