MQ-2 sensor confusion (possibly more)

Other Hardware Sensors
1

Good day fellow Arduinerds,

I have some questions on using MQ sensors. I purchased a lot of 9 MQ sensors from Amazon (MQ-2 thru 9 and a 135 sensor). I'm going to use the MQ-2 sensor as the example here. In my research and according to the manufacturers datasheet (https://www.mouser.com/datasheet/2/321/605-00008-MQ-2-Datasheet-370464.pdf), the very first complete (and only) sentence under the "Applications" section, specifies the sensor is used for detecting: LPG, i-butane, propane, methane ,alcohol, Hydrogen, and smoke.

So with a bit more research and checking YT, I noticed that the MQ-2 sensor was being used for LPG, Smoke (which was fine), and .. CO, which... I can't tell if it's CO2 or genuinely CO, and it's not mentioned in the datasheet. So that makes a bit of a quandary here.

So I have ask a few questions here.

1 - Those who have used MQ-2 sensors, what exactly does it measure, because there seem to be some discrepancies between the datasheet and what it actually measures.

2 - If it does measure more than LPG, Smoke, and CO (whatever CO is), can I pull that data from the sensor as well? And how would I go about doing that?

Thanks in advance for any information.

  • Josh

Edit to add: This is from the datasheet as well:

Detecting concentration scope：
200ppm-5000ppm - LPG and propane
300ppm-5000ppm - butane
5000ppm-20000ppm - methane
300ppm-5000ppm H2
100ppm-2000ppm - Alcohol

2

The MQ series of sensors all respond to a number of different gases, so it is generally not possible to use them to measure anything, unless you already know exactly which gases are present. The sensors are also unstable, so even with frequent recalibration, at best they can warn you that some component in the air has changed.

My copy of the MQ-2 data sheet (one of several different ones available) clearly indicates that the sensor responds to CO, but says nothing about CO2.

Finally, in your tests, be sure to observe the 48-72 hour burn in period, before attempting to make measurements.

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Michael Madsen's Electronic Nose project is interesting reading.

3

Carbon monoxide. A colorless, odorless gas that replaces the oxygen that your red blood cells carry to your body cells so you can keep living. Too much carbon monoxide, CO, and you are dead.

As noted, the sensor will respond to any and all the listed gases.

4

Oh I know what CO is. I just didn't know if CO was CO2 or actually CO, since the sensor datasheet is all over the map.

5

What you might expect for a $2 sensor, sold in large quantities by various obscure manufacturers based in China.

6

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