Electrochemical gas sensors—also sometimes referred to as electrochemical analyzers or electrochemical toxic gas detectors—are designed to measure the concentration of a specific gas (e.g., oxygen or carbon monoxide) within an external circuit. In the following article, we outline how they work and what gases they can detect.
Operating Principles of Electrochemical Gas Sensors
An electrochemical gas sensor generally consists of a working (i.e., sensing), counter, and reference electrode, all of which are contained within a housing with a gas-permeable membrane. During sensing operations, it is submerged in an electrolytic liquid. Combined, these components allow it to perform its function.
The housing membrane allows gas—but not the liquid—to pass into the sensor. An electrochemical reaction—either oxidation or reduction, depending on the type of gas—occurs when the gas reaches the working electrode. This reaction initiates a flow of electrons (i.e., current) between the working electrode and counter electrode. An oxidation reaction moves electrons from the working electrode to the counter electrode, while a reduction reaction causes electrons to move from the counter electrode to the working electrode. In either case, the electrical current generated is proportional to the concentration of the target gas. This current is then amplified and processed according to the calibration to give the user a reading in either parts per million (PPM) or percentage volume. If no target gas is detected, most electrochemical sensors indicate a reading of zero. However, unlike catalytic bead sensors, the sensor does require a balance or zero adjustment.
While electrochemical sensors are designed to identify a specific gas, most demonstrate some degree of cross-sensitivity. This phenomenon refers to the response of the sensor to gases other than the target gas, generally as a result of greater chemical reactivity in the non-target gas than the target gas. In some cases, the non-target gas can mask the presence of the target gas. For these reasons, it is important to employ the use of filters and bias voltage during operations to minimize the effect of cross-sensitivity on the accuracy of readings.
The rates of the chemical processes on which electrochemical sensors rely are proportional to temperature. As such, variations in temperature can affect sensing performance. For greater reading accuracy across a broader range of environmental conditions, some form of temperature compensation is recommended.
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What Gases Do Electrochemical Sensors Detect and Measure?
Electrochemical sensors can detect and measure a variety of gases—ranging from toxic to explosive to air quality—depending on the needs of the application, including the following:
Electrochemical Gas Sensor Solutions From Nova Analytical Systems
Electrochemical gas sensors find use in a wide range of industrial, commercial, and residential applications. In addition to detecting the presence of toxic gases in occupied spaces, they are used to ensure gas employed in sensitive operations remain at optimal levels. For customers in need of quality gas analyzers that utilize electrochemical gas sensors, Nova Analytical Systems is the ideal supplier.
At Nova Analytical Systems, we design and manufacture analyzers that use a broad selection of sensors, including non-dispersive infrared (NDIR) and dew point analyzers. To learn more about our product offerings and how they can benefit your facility, contact us or request a quote today.