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MQ@ Gass Sensor PPM Calculation

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bilal shareef

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MQ-2 Gass Sensor PPM Calculation

HI,
I am using MQ-2 gas sensor for calculating the gas concentration of the Smoke, CO, CH4 and propane. But i am unable to find the method to calculate the gas in ppm. I have read the datasheet but their is no help provided in it.. Please help in finding the method or formula to calculate the gas concentration in ppm. ..
 

FvM said:
How do you think to measure multiple substance concentrations with a one sensor?
Click to expand...

I think he plans to measure only one substance's concentration.

Anyway, bilal, I haven't worked with MQ-2, but I have some experience with MQ-3, and I think they are the same type of sensor. How to work with it - first you need to find the resistance of the sensor in gas free environment, and call it R0. Then, you measure resistance Rs in gas environment, and find the ratio Rs/R0. It always decreases with concentration, and all you need to do is interpolation of the data given in datasheet.
Btw, I'm dealing with similar problem here: https://www.edaboard.com/threads/303422/#post1298628
 

Than you Pero ..
this has helped me although the results are not very precise. But still they are good enough for my liking.
 

Glad I could help. Regarding precision, well this type of the sensor is not very sophisticated...though it can give you rough estimation which is quite useful in some applications.
 

I think he plans to measure only one substance's concentration.
Click to expand...
He didn't say. But to rephrase your answer, a quantitative calibration of unspecific sensor like MQ-x doesn't makes sense, if the sensor is responsive to multiple substances in the measured atmosphere. If you want to use MQ-2 as a detector for flammable gases (gas leakage detector) you'll calibrate it e.g. for propane or butane. But you should know, that the sensitivity for methane (natural gas) will be considerably lower.

The situation is even worse for those sensors that are sensitive to various air contaminants and also CO2. A quantitative calibration with this sensor type is effectively useless.
 

I totally agree. Sensor is good only for ON/OFF functions, and only for one substance, I'd say
 

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