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Erriez / ErriezMHZ19B

Erriez MH-Z19B and MH-Z19C CO2 sensor library for Arduino
https://github.com/Erriez/ErriezArduinoLibrariesAndSketches
MIT License
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Why is the value only 400ppm? #2

Closed thanapol199717 closed 3 years ago

thanapol199717 commented 3 years ago

Hello, I need help I'm not sure why Co2 is only 400 ppm, but I've tried mouth-watering. The value has changed, I'm not sure if my sensor is normal. image

Thanks in advance for the answer

thanapol199717 commented 3 years ago

Sorry, last time I sent it to DHT 22.

Erriez commented 3 years ago

@thanapol199717 Did you try to power the MH-Z19B sensor continuous for more than 5 minutes? It takes some time before the sensor generates valid data and is normal behavior. You can try to blow into the sensor a couple of times which should increase the value. Is that what you mean with mouth-watering?

Another suggestion is to check the calibration mode. Automatic baseline calibration is executed every 24 hours and requires around 15-30 minutes in fresh air once a day or week for good calibration results.

Note: 400 ppm is the minimum CO2 value of outdoor air.

thanapol199717 commented 3 years ago

Thank you very much for you answer me.​ oh, it means blow.​ I blow it and it changed. Is my sensor normal?

Erriez commented 3 years ago

oh, it means blow.​ I blow it and it changed.

No problem :-)

Is my sensor normal?

It takes time before the value changes (around 30..60 seconds minute) and that's normal. I suggest to put the sensor in a room with doors/windows closed and measure/log the CO2 values when at least one person is inside the room. Test the sensor with >24 hours powered. After a couple of hours, the CO2 value increases. A value of 400ppm is outdoor clean air, above 800ppm indicates that the room needs ventilation, above 1200 is unhealthy and above 2000 is dangerous. Success!