Which sensor type is commonly used in alcohol measurement and is electrochemical?

• A. Fuel cell
• B. Infrared detector
• C. Thermal detector
• D. Optical sensor

Answer: (A)

The key idea here is that alcohol measurements commonly use a sensor that converts a chemical reaction into an electrical signal. A fuel cell sensor does exactly that: ethanol from the breath is oxidized at the anode, producing electrons that flow through an external circuit and generate a current. The size of this current is proportional to the ethanol concentration, giving a direct, electrochemical readout. This approach is favored for alcohol measurement because it’s relatively selective for ethanol, works well in portable devices, and doesn’t require bulky optics or heating elements.

Infrared detectors rely on measuring ethanol’s light absorption at specific wavelengths, which is a spectroscopic method rather than electrochemical. Thermal detectors respond to heat changes rather than chemical reactions, so they don’t provide the direct chemical-to-electrical signal used for ethanol quantification. Optical sensors use light in various ways but do not inherently measure the chemical current produced by ethanol oxidation.