MQ-3 Alcohol Measuring Module

MQ-3 alcohol sensor module for measuring alcohol vapor concentration in air. The MQ-3 is a gas sensor module used in breathalyzers and environmental monitors to detect ethanol alcohol vapor in the air.It contains a tin dioxide ($SnO_2$) heating element whose electrical resistance drops when it comes into contact with alcohol gas. The module converts this change in resistance into both a 0V to 5V analog voltage signal—which tells you the relative concentration of the alcohol—and a digital high/low signal for simple threshold triggers. It operates on 5V and requires a built-in heater to warm up before it can provide accurate readings to a microcontroller.