Need help converting brick board MQ-7 sensor to PPM values

End-Of-Life Products & Services Tech support before 2012
#1

Hi guy,
I bought a Temperature sensor brick board (seeedstudio.com/depot/electr … p-470.html). It connects fine and and data is flowing through nicely, however all my values are for e.g:
150
152
151
149
152
…
…

Can someone help me to calibrate the POT and write a code for calculating the PPM values?

THANKS!

#2

Please refer to this datasheet:http://www.hwsensor.com/English/PDF/sensor/MQ-7.pdf

Thanks!

#3

I’m not an expert and I don’t understand this datasheet :confused:
This is my first time working with elettronics component and I cannot find the system that generating code.

Can you help me?

#4

frist , transfer this data to a voltage value : if you use the Atmega 168 and ues the 5V standard, then 150 *5V /1024 = 0.73V

The surface resistance of the sensor Rs is obtained through effected voltage signal output of the load resistance RL which series-wound. The relationship between them is described: Rs\RL = (Vc-VRL) / VRL

And you need to test the sensor resistance at 100ppm CO in the clean air , then you can check the diagram Rs/Ro to work out the ppm.

take note of that : the sensor need to be warm-up more than 48 hour ( Turn on the power, keep preheating through electricity over 48 hours)

#5

If you just want to do an alarm check, which only a rough threshold is needed, you could measure the voltage of corresponding environment, and use this value to judge.

This is a industrial level sensor, some calibration is needed to get precision.

#6

…sorry but what can I do to test the sensor at 100ppm if I don’t know the values before that? Can I understand that the air is clean without the sensor works right?

Thanks

#7

Hi Esp,
thanks for your suggests, but I need to get the ppm values number because I’m going to interfacing my seeeduino board with pachube.com sharing website. :wink:

Regards.

#8

i think the Ro that the sensor resistance should be in the datasheet befor , but i can not found it there… and the datasheet suggest that to adjust it in 200ppm , so i think it means that you need to do this include getting the Ro … "how to test the sensor resistance at 100ppm ", i am not very sure that , so sorry cann’t give you more help.