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metriful / sensor

Sensor by Metriful | Indoor environment monitoring | Documentation and code samples
https://www.sensor.metriful.com
MIT License
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AQI accuracy & P2 from PPD42 #1

Closed Sennevds closed 4 years ago

Sennevds commented 4 years ago

Hi,

Really love the board and I got everything up and running and sending data via MQTT to my Home Assistant. Only have 2 questions:

  1. I can't get the AQI accuracy above 1 it's most of the time 1 and sometimes even 0. I've already blow on the sensor but it looks like nothing works
  2. The PPD42 has a port 2 if you like at this https://github.com/mauricecyril/pidustsensor it's used for reading PM1.0 values. Is there an option to use this port?
metriful commented 4 years ago

Hello!

  1. It can take a long time, especially for new sensors (there can be a "burn-in" time for stabilization). It is important to keep the sensor running frequently (use 3 second cycles). Expose to clean air and dirty air, for example alcohol vapor.

  2. The MS430 board has a single input for particle sensing. You can connect it to the PPD42 pin 2 instead of pin 4, both pins use the same output signal method. However, the manufacturers do not give much information about pin 2 or the related threshold input on pin 5.

Sennevds commented 4 years ago

Thanks for the answers. The accuracy went after 5 hours to 3 and then after a few hours back to 0. Is this normal? I have the refresh on 100sec at this moment. For port 2 I understand. Going to see if I can find more info on this.

metriful commented 4 years ago

When the accuracy went from 3 to 0, did the MS430 board exit cycle mode, or could it have been reset? If either of these happens, the calibration starts again from accuracy 0.

metriful commented 4 years ago

To summarize the accuracy value:

It can take several hours for a new sensor to stabilize and go to higher accuracy. The stabilization will be faster if you use a shorter cycle time. As the sensor ages it should be quicker (impurities on the gas sensor are "baked out").

If you exit cycle mode, or reset the board, it will start again from 0 and needs to recalibrate again. Otherwise the accuracy should rarely return to 0 after going to 1.

If it remains 1 for a long time, expose the sensor to a marker pen, alcohol etc. The AQI should go to about 500 and then the accuracy will go to 2.

The accuracy will slowly alternate between 2 and 3, this is intended. It can occasionally go back to 1 or 0 (rare).

Sennevds commented 4 years ago

For me it variates between 2 3 and 1. It's running constantly with a cycle of 100sec. You can find my code I use here https://github.com/Sennevds/sensor/tree/master/Home_Assistant I don't think I do anything special. When I'm back from my holiday I'm going to make a separate sensor for the accuracy so I can better track the values.

metriful commented 4 years ago

OK, that sounds like normal operation.