search

ostaquet / Arduino-MQ131-driver

Arduino driver for gas sensor MQ131 (Ozone / O3)
MIT License
64 stars 19 forks source link

About the influence of temperature and humidity in the values. #18

Closed ferreiradiego closed 4 years ago

ferreiradiego commented 4 years ago

In your study, do you realized that the temperature and humidity influence a lot in the concentration values of O3?

I did that question, because I am studying this sensor MQ131 (Low Concentration) and seems to me that the temperature and humidity do not influence a lot in the values.

Congratulations for your code, it's excellent

ostaquet commented 4 years ago

The temperature and humidity influence has been designed based on data sheet details on page 4.

The formulas have been designed based on the sensitivity curves.

ostaquet commented 4 years ago

Additional comment on this, @nitram147 fixed some bugs in the calculation of the environmental correction. Please use the v1.4.0 to have the last version.

ferreiradiego commented 4 years ago

Hello @nitram147. Could You explain to me why the value of resistance is divided by the value of getEnvCorrectRatio()? As in the line code correctedValueR0 = _valueR0 / getEnvCorrectRatio();. My doubt is about how the resistance ratio is corrected, is the code to correct the ratio only a mathematical artifice?

PS.: I'm doing a study about MQ Sensors and the more details I get, the better will be my study.

ostaquet commented 4 years ago

The idea is to compare apples with apples. ;-)

According to the data sheet, the resistance of the sensor is affected by the temperature and humidity. This impact is implemented with the corrective ratio coming from getEnvCorrectRatio().

But... this should be in the calibrate() function and not in the setR0().

ostaquet commented 4 years ago

It is quite a good question...

At the moment, the correctedValueR0 is defined when the setR0() function is called. According to me, it is not exactly correct.

The R0 should be adjusted when we calibrate the sensor and when we get the R0 value (because the R0 value evolved with the environment).

ostaquet commented 4 years ago

I dig a bit deeper in this and there was an error in the code uploaded before. Sorry about this.

If we look carefully to the data sheet, we can see that the environmental corrective ratio has to be applied on the Rs/R0 ratio and not on the measurements of the resistances.

image

It is fixed in v1.4.1.