i wish to ask about the MQ-4 gas sensor
how to differentiate it is left side or right side?

 

So you have a datasheet?

I'm betting the text is the trick, that or there is a notch somewhere you can't see in the picture.

 

Hello,

The datasheet can be downloaded here:
http://www.hwsensor.com/English/products/sensor/Semiconductor.htm
http://www.hwsensor.com/English/PDF/sensor/MQ-4.pdf

Bertus

 

yes, i have a datasheet.
but the datasheet does't show where is the front of the sensor.
so i can't get where is the left side and where is the right side.

 

Look at the text, one side is up, the other side is down. This defines a left and a right.

 

this is means, now im facing the side of sensor which have label MQ-4 there and i turn around will be plan digram in configuration B?

 

The way you have it shown in the picture on post #1 is the same as shown in Config B

This will show you connections:
www.pololu.com/file/download/MQ4.pdf?file_id=0J311