Datasheet for the MQ-3 gas sensor, a tin dioxide semiconductor sensor sensitive to alcohol vapour, widely used in breathalyser kits and hobby modules. The short PDF covers heater voltage, load resistance, sensitivity curves, preheat time and the basic measurement circuit. A technician uses it to check heater current and sensing resistance when a module gives unstable or no readings. Allow the specified warm-up period before judging the sensor, and note readings depend strongly on temperature and humidity.
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