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Author Topic: Carbon Monoxide Sensor - MQ-7 Output and scale  (Read 301 times)
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I am using a MQ-7 with Arduino to detect Air pollution.

But, is there a scale or a scientist Table to define Air quality based on sensor's output?
when Air quality is good and when it is bad?

Thanks
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No, you get a number of the analogRead(), and after a while you will know when the air is good or bad.
The resistance of the sensor changes according to gasses in the air, that's all.
You have to use the preheat and so, see this page:
http://playground.arduino.cc/Main/MQGasSensors
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The output from the sensor is meaningless without proper calibration against known standards.
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Calibrating this sensor is useless, because it is ment to detect air polution and not an amount of a specific gas.
Since it detects a combination of gasses, the output is an indication for the polution.

On the other hand, this sensor is very sensitive, and small amounts of strange gasses can be detected. So it can be useful to detect "something". You will never know what that "something" is and in which amount.
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Thank you all.
So I can't classify outputs recording to pollution degrees ,?, I can't just know if there is gases in air and basta? 
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This sensor measures the ammount of carbon monoxide in ppm, but this is only if that is what you have. It will not detect CO1 from a mixture of gasses like CO2 and alcohol vapour.
There are recognised levels of CO1 in PPM that are considerd safe.
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You can make up your own polution degree.
If you test the sensor with a know concentration of gas, you can use that.
But it will also detect other gasses, but perhaps that is not a problem.
There are also other sensors for carbon monoxide.

A cheap MQ-7 sensor can be used after all, but don't expect a reliable output.
« Last Edit: January 26, 2014, 02:54:40 pm by Caltoa » Logged

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