PreHeating Process Of MQ135

Its my first time working with analog sensors. And I have few doubts.

What do you EXACTLY mean by pre-heating?

Is it leaving the sensor on for 24 hours (For MQ135). 24 hours because its mentioned in the datasheet.

Do I have to do something else when I leave the sensor on for 24 hours. I am planning to just make a simple connection with Arduino Uno and the MQ135 sensor and leaving it on for 24 hours in fresh air.
Connections: Ard A0 to Sensor A0
Ard VCC to Sensor VCC
Ard Gnd to Sensor Gnd
the code will be simply taking raw values of the sensor. No calibration nothing for now.

I just want to know pre heating means leaving it on for 24 hours right? Nothing else right? Because there is no articles actually mentioning how do you pre heat sensors! PLEASE HELPP!!!!

How to Use MQ-135 Gas Sensor? – ANAVI Technology may help

I have already read this Article...

It says this - "As explained in the video and shown in the datasheet of the sensor, MQ-135 requires calibration. At first launch the so called “burn-in” (or preheat) procedure must be performed by leaving the sensor working for 48 hours in a room with a clean air."

Again my question is exactly how and what to do? Just leave the sensor on for 24 to 48 hours?

That is what is implied at about 3:35 in the video

The initial preheat is to form the tin oxide that will be used later to do the sensing. So, it is a one-time process. Also be aware of this: "After the sensor is energized, it needs to be preheated for about 20S, and the measured data is stable. ". All depends on what you are doing with the sensor.


So I just have to leave it on for 24 to 48 hours, right? For correct values

Thank you.

AND then preheat for 20 seconds before beginning to take readings each use.

Thank you for your guidance! Much appreciated

You should find the Electronic Nose tutorial by Michael Madsen informative, where he extensively discusses the preheating, and proposes some very interesting applications.

It is off line, but copies can be found on the internet archives.