CONVERTING ANALOG OUT OF MQ-7 TO PPM

Hi guys.. Can somebody help me how to convert the voltage out of MQ-7 to ppm? I already do the cycle time,interface it in arduino board and received a analog out from the sensor.But the problem is i dont know to convert those output to a useful one or ppm values.can somebody help me or give me an idea?

hi!

is it this one: http://www.sparkfun.com/datasheets/Sensors/Biometric/MQ-7.pdf ?

did u heat it properly?

then u need to measure the resistance of the A and B pins... u can do it in 2 ways: 1. send a known current through it (e. g. 50uA) and measure the voltage at the A and B pins... 2. send a known voltage via a known series restistor through it (e. g. 100kOhm) and measure the voltage at the A and B pins...

have fun... :)

yes.im using that one.you mean preheating the sensor in 5v(60sec) and 1.4v(90sec)? or preheating it with 5v in less than 48 hours? the A and B pins of the sensor? thanks for your reply.. :)

1. i think for moderate accuracy preheating with 60sec@5V should be sufficient... 2. yo... A and B...

thanks. do you have any code?or idea? coz i will display it in LCD.

hm i never did it myself...

maybe this works fine: hardware: +5V(from arduino) -- pin A GND(from arduino) -- ~10kOhm resistor -- pin B it seems like the heating voltage affects the resistance between pin A and pin B...

software: measure the voltages at pin B with an analog pin... http://arduino.cc/en/Reference/AnalogRead regarding the LCD: http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary

interpretation of the readings: u will need reference concentrations... but be careful: CO is dangerous to humans and animals... so u should possibly do it together with a teacher who smokes (cigarette smoke contains CO)... but: smoking is not necessarily healthy... :) then u should c a change of voltage... but then u wouldnt know how much CO it was... :-) maybe u know a firefighter? they might have calibrated CO meters...

thanks again.. i already have the conversion code and i was able to display it in lcd.but the main problem there is that i dont know if the reading is accurate. :) so same with your suggestion i used a cigarette. :) i will try another method