Interpreting MQ-9 Carbon Monoxide Sensor Results: Understanding 0.41V Output

Hello

I bought a CO sensor (MQ-9) and other gases such as this:
https://botland.com.pl/czujniki-gazu/3029-czu...-latwopalnych-gazow-mq-9-modul-niebieski.html
After connecting to 5.37V and stabilizing the output on the analog, it shows me 0.41V (i.e. about 8% of the supply voltage).
Should I interpret this as 80 ppm CO in the air ??
I don't know how to read this documentation:
http://www.haoyuelectronics.com/Attachment/MQ-9/MQ9.pdf

Phantom

These sensors must be calibrated with a reference gas. they are not suitable for measuring applications.

Quote:

After connecting to 5.37V and stabilizing the output on the analog, it shows me 0.41V (i.e. about 8% of the supply voltage).
Should I interpret this as 80 ppm CO in the air ??

It's not that easy.
First, it is not a sensor for precise measurements, but it is cheap and has good sensitivity.

First, the sensor must be heated in clean air, the manufacturer tests after 48 hours of heating.

As the colleague above writes, calibration should be performed, but without it, the concentration can be (very) approximated.

After heating, the sensor will have some resistance in clean air R0, it is not specified in DS, because it is subject to large production spreads.

From Fig 1 it can be read, for example, that for 1000ppm LPG the resistance will be ten times lower than in clean air.

The sensor resistance must be calculated from the voltage - you need to know the value of the resistor (Rl) on the board.

The manufacturer of the sensor recommends changing the voltage on the heater periodically, your module does not have it, it can be done on the LM317 or other adjustable stabilizer. CO detection at low heater voltage, other gases at high voltage.

Oh people
I guess I'll let it go. I thought it was a more human-oriented module.
Generally, I am looking for something that will tell me, even on a few scale, how much CO is in the air. So, a typical home carbon monoxide detector, but not only 0/1.
Thanks for the info.

Phantom

szczukot wrote:

Generally, I am looking for something that will tell me, even on a few scale, how much CO is in the air.

You chose well, but you have to try harder.

Electrochemical sensors are better (more accurate, more selective), but they are more expensive and have a limited life time.

jarek_lnx wrote:

You chose well, but you have to try harder.

bezedura ..

Temperature and humidity tolerances as well as the stability of semiconductor sensors, especially at low concentrations (below 100ppm), are simply embarrassing, especially as their measuring range often starts from several dozen ppm, which in the case of CO is a death threat.

Added after 2 [minutes]:

jarek_lnx wrote:

After heating, the sensor will have some resistance in clean air R0, it is not specified in DS, because it is subject to large production spreads.

after 1 log (0) is? I'm curious. In clean air, the indication fluctuation + environmental dependency will be so much of hoho

Well, I probably give up calibrating it

Phantom