Help with methane gas sensor MQ-4

Using Arduino Sensors
1

Hi, I need your help. How can I transform the value analog output voltage (0 to 1023) to PPM (parts per million)?

2

You have to first "burn in" the sensor for 72 hours or more, as described in the MQ-4 data sheet, then calibrate it by exposing it to known concentrations of methane in dry air.

The sensor responds to other gases, which if present will make the calibration useless.

3

Thank you. But, how can I show, mathematically, the result (analog value) in PPM?

4

To convert analog readings to PPM, you use the scale factor and offset that you determine when you calibrate the sensor.

float ppm = scale*analogRead(pin)+offset;
5

Seems the sensor is not that linear (never used one).
With the graph from the datasheet you can try to convert to PPM with multiMap, before final calibration.
Leo..

6

The nonlinearity in response is the least of the sensor's problems.

7

I’d agree - these are really combustible gas sensors , they suffer with drift and don’t return to the same output after detecting gas ( esp high concentrations ) . I would only use to detect a rapid change where absolute values don’t matter .

8

Thanks!!