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Topic: MQ3 Values question (Read 198 times) previous topic - next topic

gongassx

Hello,im a student and im developing a breathalyzer as my project the code is done but i got a little problem, i cant figure out in what unit of measurement the sensor detectes the alcohol when i look at the display or at the serial monitor it only says for example "Alcohol value 245".
I read the datasheet for the mq3 sensor but i still cant figure it out, also how can i translate that value to bac?
I really would appreciate some help on this one haha,well thanks in advance!

jremington

#1
Jun 14, 2020, 03:45 am Last Edit: Jun 14, 2020, 03:47 am by jremington
The sensor output has no units, and requires calibration.

To calibrate, you first have to expose the sensor to clean air and burn it in for up to 72 hours (as described in the datasheet). Then you expose it to one or more samples of air containing known percentages of alcohol, and note the sensor readings. From those readings you can derive a calibration factor.

Adafruit has a good general tutorial on sensor calibration.

Keep in mind that all the MQ sensors respond to several different gases, and cannot distinguish between them.

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