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hello sir, i have a project and it is measurement of ammonia gas sensor for poultry industry. I bought an ammonia sensor MQ-137 ammonia sensor with sensor module from goodluckbuy.com.
i interface this to arduino but the problem is i dont know how to calibrate this sensor. i have measured voltage that came from the serial monitor.
what is written in the datasheet are the sensitivity of the sensor Rs/Ro vs ppm. how can i used this value to calibrate my sensor so that my measurement for ammonia will be accurate.
What voltage changes are you getting? If you test the voltage out in air only... This will be your zero... Then work out using the equation in the data sheet the MAX voltage.. Use a software map to Display your readings
hello sir, Base on the figure that you posted, i try to use the graph Rs/R0 vs ppm I computed the output voltage for 10 ppm. please tell me if I am wrong with these calculation:
Based on the graph the ratio of Rs/R0 = 1.5 for 10 ppm ( Nh3 data) and i manipulated the formula to find the Rs, which is Rs = 1.5(Ro). From the datasheet I used the lower value of R0 (from 900k - 4.9 Mohm). I used 900k as the resistance of sensor in clean air. THen I got 1.36 Mohm value of Rs coming for Rs = 1.5Ro.
Then i used voltage divider formula to find the output voltage. for the voltage divider the formula is
Vout = Vc( Rl/Rs + Rl)