3 ms·

I don't see any benefit in this product having two identical sensors side by side. Based on the datasheet, the reading between sensors is quite consistent, mean

I don't see any benefit in this product having two identical sensors side by side. Based on the datasheet, the reading between sensors is quite consistent, meaning that there's no improvement in accuracy. What would be better is to have two different sensors, one of which actually counts PM 10.0. A little-known fact about these air quality sensors is that they don't actually measure three different particle sizes, they typically measure the smallest one and then return some statistically determined value for the larger ones. [1] https://www.digikey.jp/htmldatasheets/production/2903006/0/0/1/pms5003-series-manual.html https://www.digikey.jp/htmldatasheets/production/2903006/0/0...

ahaucnx 3y ago
There are two main advantages of having two sensors: a) Data quality: You can detect if one sensor fails as the two readings will start to deviate and then replace the faulty one b) Extend the life of the monitor: The PM sensors with the laser and optics have a limited life. By having two inside, you can alternate the measurement and put them in sleep mode inbetween. Thus extending the life of the monitor.
- cyberax 3y ago
  Just a note: can you stagger the sensor time a bit unevenly? Instead of 50%/50% time split, can you do something like 40%/60%? This reduces the risk of both sensors failing at once because they have approximately the same duty time.
  - jeffnappi 3y ago
    Considering it is open source, you could do this :)
    - cyberax 3y ago
      I've just ordered a device, we'll see.
- deleted 3y ago
  [deleted]
- codetrotter 3y ago
  > You can detect if one sensor fails as the two readings will start to deviate and then replace the faulty one But how do you know which one is the faulty one?
  - ted_dunning 3y ago
    The failure modes are commonly fairly apparent. One sensor will go to a static low value and the other will show normal variability. In the theoretical limit of all mathematically possible failure modes and all possible environmental conditions, this would be impossible of course. But we live in a fairly predictable environment and the nature of the failures is not unlimited. As such, it is pragmatically pretty easy to see the difference.
trailbits 3y ago
My outside sensors sometimes get contaminated from pieces of spider webs. It can be really hard to distinguish this from otherwise dirty air in a single sensor system, but when you have two you know something is wrong with one of them. A quick clean with the vacuum and both agree again.

ahaucnx 3y ago

There are two main advantages of having two sensors: a) Data quality: You can detect if one sensor fails as the two readings will start to deviate and then replace the faulty one b) Extend the life of the monitor: The PM sensors with the laser and optics have a limited life. By having two inside, you can alternate the measurement and put them in sleep mode inbetween. Thus extending the life of the monitor.

cyberax 3y ago
Just a note: can you stagger the sensor time a bit unevenly? Instead of 50%/50% time split, can you do something like 40%/60%? This reduces the risk of both sensors failing at once because they have approximately the same duty time.
- jeffnappi 3y ago
  Considering it is open source, you could do this :)
  - cyberax 3y ago
    I've just ordered a device, we'll see.
deleted 3y ago
[deleted]
codetrotter 3y ago
> You can detect if one sensor fails as the two readings will start to deviate and then replace the faulty one But how do you know which one is the faulty one?
- ted_dunning 3y ago
  The failure modes are commonly fairly apparent. One sensor will go to a static low value and the other will show normal variability. In the theoretical limit of all mathematically possible failure modes and all possible environmental conditions, this would be impossible of course. But we live in a fairly predictable environment and the nature of the failures is not unlimited. As such, it is pragmatically pretty easy to see the difference.

trailbits 3y ago

My outside sensors sometimes get contaminated from pieces of spider webs. It can be really hard to distinguish this from otherwise dirty air in a single sensor system, but when you have two you know something is wrong with one of them. A quick clean with the vacuum and both agree again.