After reading the datasheet, Do you think that if i need to measure the CO and not the methane, I just need to apply the low heater voltage and not both of them ????
The datasheet for the newer MQ307A shows how to set its heater to measure CO and methane, but it doesn't say anything about your older sensor.
You should be using a modern sensor and have a datasheet and application notes for it. It would explain if you need to swich the heater voltage high and low and explain why. It would have cautions about exposure to the deadly gas. It would explain if its accuracy is affected by some of the many other elements in an engine's exhaust including its temperature. It would show how to calibrate it.
I 'assumed' that testing in a well ventilated area (eg OUTSIDE) would be just like standing next to a car while its engine is running (since he is using an engine exhaust to provide the CO)
HEY, I now have the data sheet (in full) for the MQ307A sensor, which I have attached. Hope this helps you to understand how the sensor works, and how to connect it.
You just need to email hanwei and ask them to mail it to you. . . that's all I did. Go to their web site and the email link is there, just ask for the data sheet. It took 3 days for them to reply to me.
I emailed them last week and still no reply :'(
I asked for the MQ307 and not for the MQ307A .
the MQ307A is posted on the website while the MQ307 No
Anyway I was able to find the MQ307A but still need some documentaion on it :'(