I have used the SDS011 for PM and DHT22 for temperature/humidity for about two years. Since the beginning of November, the SDS011 sends implausible values, practically 0. A restart does not bring anything, a longer break also nothing. The fan continues to run, the measurement cycle remained unchanged. No connection problem, sensor is accessible
So I have now installed a new sensor, works again with plausible measurement results: how to increase the life? Or was I just unlucky?
Second point: the DHT22 is useless for humidity measurements, always shows 100% in winter. The same with a replacement sensor. A BME280 solves the problem, I have done the same with the exchange of the SDS011.
The SDS011 is not ment to be used outdoors. So I think that’s why you won’t get the expected lifespan. Two serviceable years of operation is quite nice i think.
The DHT22 is also not designed for usage outdoors…
SDS011 is /cheap/ at around $20. Keep in perspective that many commercial systems sell for $2000-$5000. The SDS is used in many commercial systems like the aeroqual which is manufactured in california. It’s a fine little instrument and a bargain. Estimated life is 3 years, or about 300 hours of sniffing. Main impediment to accuracy is getting a good humidity reading. Out of the 30 or so that I have bought two had high readings out of the box, and one just went tits up with zero readings. So, maybe 1:10
DHT22 should be replaced by BMP280 which includes air pressure. Lukas was pretty adamant about this. I have been upgrading my sensors and tossing the DHT22.
I paid more than $20 for the SDS011, but no matter, that’s just the maintenance cost for the sensor set.
The BME280 really gives much better results than the DHT22 in terms of humidity. Is really worth its higher price.
By the way, the sensors are mounted as often suggested, protected in two 90° 70mm PVC pipe bends and in the shadow of a large parabolic antenna.
My SDS012 is now almost 4 years old and still no problems.
The sensor is indoors with tube going outdoors.
I also use a BMP280 in conjunction.
I replace this sensor regularly once a year.
Best is to locate SDS011 indoors for greater lifespan.
I have now the third SDS011 sensor. First one lasted about 1.5 years after that it had constantly too high values. Second sensor lasted about 2.5 years and had, like yours, constantly too low values.
Sensor was mounted directly under a roof next to a massive wall. So no rain could reach the sensor. At that place it was about 2 to 4 degrees warmer because of the proximity to the wall. Still sensors didn’t last very long. So I can confirm your experience.
I was also worried about a few SDS011 which constantly read too low compared to a well working sample, which gives results very close to the next official station.
As the data was qualitatively OK (i.e. the shape was right) but just quantitatively off, I added a scaling factor.
Sample result from the past 2 days:
SC (SDS) - SDS011 SensorCommunity built, no heating
NAM (SDS) - SDS011 in NAM case with heating and a scaling factor of approx “2”
SC (SPS) - Sensirion SPS30 in same casing as SC (SDS)
NPM 2.5 - Tera NextPM with internal heating
(data shown has been smoothed via moving average of 5 values)
My 2 cents:
- scaling factor works at least in my case
- heating does not have a visible effect
- note for @pjg : NPM with fulltime option did not have a visible effect but the sensor sounds much healthier with the fan not running all the time
I’m comparing one SDS011 with an Ecowitt (link) and the result is an average difference of 52%. But I do not have a certain reference that allows us to understand if WH41 overestimates or SDS underestimates.
You have been able to adjust one to their own average.
Maybe i need to add more SDS011 sensors to not suffer the potential error of a single (maybe i have the worst and i don’t know)
It’s not just adjusting one to the average, it’s adjusting one SDS to the other SDS which is close to the official data.
Here is an example from last week. Orange is the data I scrape from the official sensor’s website. It does not update between 21:00 and 4:00 but for the rest of the day the agreement is usually quite good.
The peaks are caused by my neighbour burning old furniture and parquet.
right, I didn’t understand that you also have the reference data.
I am missing a reference point to considere in my compare.
The closest reference sensor is at 8.6 km and makes only one data per day at 23:10.
The distance is about 4km over here… not perfect but depending on the weather it’s a good match.
It’s a pity you get just one value per day. Where is it located? Any chance to talk to the operator and ask for more data? I was surprised that over here I got a quick response and they added PM2.5 to the summary view on their website (was just PM10 before).