Hey guys. I want to design a gas detection sensor (multiple devices for multiple gasses for example LPG, Smoke, Air quality and ...).
i searched for Senors and i fount out the MQ series are the most common in the market. but are they reliable for a product? how should i calibrate these series? Do you offer any kind of different sensors?
Thanks for your reply.
Found this thread for calibrating but are these series are reliable for a product?
Calibration procedure of a MQ135 | All About Circuits

 

I will share this much. The subject comes up frequently and while the MQ series of sensors does work they are pretty much limited in scope to hobby applications. Calibration of actual gas sensors requires calibrated samples of the specific gas in question and those samples are expensive. Also things like temperature compensation play a role in results. Just for example the popular MQ135 sensor:

What does MQ-135 measure?

For monitoring the air quality, a gas sensor, MQ135 is used. It measures the level of NH3, NOx, alcohol, Benzene, smoke, CO2 in air.

With that wide range how accurate do we think it will be? They cost about $3.00 USD or less so we can't expect too much from them. If you just want to see some very rough numbers yes you can connect one to a uC (micro-controller) but don't expect much.

Just My Take
Ron

 

Thanks for your reply. I don't want to read the exact ppm value, I just need to if there is CH4 (for example) in the air, uC trig the alarm system. so, by your description and the previous topic its ok to use for this purpose.

 

Thanks for your reply. I don't want to read the exact ppm value, I just need to if there is CH4 (for example) in the air, uC trig the alarm system. so, by your description and the previous topic its ok to use for this purpose.

With that in mind an inexpensive MQ4 sensor should work, nothing super accurate but will respond to methane gas. Just take the analog out and run it to analog in of a uC and set your threshold in code for a digital write out.

Ron