Ethanol-vapour gas sensor

A gas-phase sensor, not an alcohol meter for drinks

An ethanol-vapour gas sensor is an electronic instrument that responds to alcohol present in air. It belongs to gas sensing: its target is in the surrounding gas phase, such as vapour in a headspace, rather than ethanol measured directly in a beverage sample. The source material that motivated this entry flags low-cost gas sensors as possible process monitors while warning that they do not directly determine liquid alcohol by volume.

The equipment name covers more than one sensor design. Winsen's MQ-3B and Figaro's TGS2620 are contemporary manufacturer examples marketed for alcohol or organic-vapour detection. They show how a small component may serve in a detector circuit, but neither manufacturer's product information establishes a validated kombucha ABV test or a common design for every alcohol gas sensor.

How a semiconductor example responds

In the MQ-3B example, Winsen identifies tin dioxide as the sensitive material. The manufacturer's manual describes its conductivity changing when alcohol gas reaches the sensing element; supporting electronics turn that change into an output related to gas concentration. Figaro documents another alcohol-vapour sensor, with its own target range, package and application guidance. These examples are useful for recognizing the equipment class, not for assuming that a low-cost module is selective to ethanol under every condition.

A sensor signal is shaped by the model and the surrounding sample environment. The cited manufacturer documentation reports temperature and humidity dependencies, and Winsen warns that some contaminants can affect performance. In fermentation-related use, other volatile compounds, the composition and exchange of the headspace, and calibration for the intended matrix further affect what a response can mean. The reading is therefore a model- and context-dependent gas-phase signal.

Different instruments answer different questions

A carbon-dioxide probe measures CO₂; it is not an ethanol sensor. A bubble counter instead registers individual bubbles interrupting an optical beam as they pass through a liquid column. Those are different observations: gas composition, gas concentration and bubble count should not be treated as interchangeable measurements. A [bubble counter](/equipment/bubble-counter) can be compared with a vapour sensor as a separate measurement approach, but neither signal by itself states beverage alcohol by volume.

For kombucha, a validated analytical method is a different category of evidence. Chan and colleagues validated headspace gas chromatography with mass-spectrometric detection for quantifying ethanol in kombucha. That is a laboratory assay for beverage ethanol, whereas an inexpensive semiconductor component reports its gas-phase sensor response. Do not convert the latter to a drink's ABV, or use it to infer safety, unless the complete measurement method has been validated for that beverage and purpose.

Form, date and geographic limits

The MQ-3B product image shows a small packaged sensor element with a perforated cap and electrical pins; that one component is not a complete fermentation control system. The manufacturer's 2018 manual version documents a modern model, but it does not establish when alcohol gas sensors first appeared. The inspected sources also do not identify the MQ-3B's manufacturing site or establish a traditional regional use of the instrument. This page therefore records an unknown origin rather than treating a manufacturer name or a source website as proof of where the product was made.