Which sensor to use??

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Hi all

recently i was asked to build a project where the client needs to measure certain different gases(namely CO2,CO,NO,VOC,O3) presence in ambience & upload the measured values(in ppm/ppb)to a IoT server for further processing.

Now for this purpose,will the commonly available MQ series sensors do any good?What i can understand from a rough google search that they are good for detection.But can they be used for a standard(not very precise but reasonable) measurement?

If not,then what sensors to use?Please give me some advice.

 

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Looking at the schematic for these, there is an analog output

in addition to the digital (alarm) output.  The digital output is

from a comparator with a fixed (adjustable) voltage on one

input and the analog input on the other.  So if you feed the

analog voltage directly into the ADC of your microcontroller,

you should be able to take measurements.  No clue if they're

linear or very precise though.

 

--Mike

 

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You mention a ‘standard’ measurement. You need to find out if there is an applicable standard and what it entails. You need to be careful that your sensor is not required for safety purposes as this may have legal and special design requirements.

Having said that,the style of sensors you mention are widely used in industry. There maybe cheap copies of the figaro brand sensors, so if you want quality, be sure that you get known brand items. To test them you can get test gasses-but these may be expensive as they are used to calibrate the safety gas detectors used in petrochem and mining. For consumer grade testing you might be able to get aerosol cans of test gas. Google is your friend here.

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Although I do not have quality experience with MQ series sensors and none with figaro sensors, I still feel that MQ series of sensors are ok for some education but would not trust them for an implementation. I had used one of their sensor ( MQ9, I think) for CO measurement as a part of my university coursework. It was easily interfaced with Arduino, the idea was to just demonstrate detection of high concentration of CO.

 

Whether with MQ or with figaro, you still need to quantify the test results.