MQ4 and MQ7 Sensor module

Other Hardware Sensors
1

Is there here that can explain how to calibrate the MQ4 and MQ7 sensor module?

2

Put the sensor into a chamber with know gas concentration, save the value you read. Put it into a chamber with a different known gas concentration, save the value you read. You now have the base for logarithmic curve as shown in the datasheet.

Don't expect too much accuracy from these sensors as they are meant to detect if there is no gas, a low concentration of gas or a high concentration of gas. They are not designed to provide PPM values (which isn't possible either because they react to various gases.

3

thanks. Do you know how to get the ppm value? (Although less accurate)

4

Do you know how to get the ppm value? (Although less accurate)

Exactly as I wrote in my answer. The problem is that you don't actually get PPM values as the sensor reacts to several gases and you don't know which combination of the gases you have. If you have a controlled environment where you know that only one of the gases exist, you can use above procedure to get an approximation of the PPM value.