DSM501 Dust and Particle sensor accuracy

Hello,

I am using the DSM501 Dust and Particle sensor for the first time with code from Calculate the Air Quality Index (IAQ, IQA) with a DSM501 on Arduino or ESP8266 • DIY Projects.

I am getting some values for PM 2.5 and 1.0 but am not sure how accurate they are. For example, my dad uses a air purifier in Delhi and when it is turned on it shows 120 or 150 say, and then after running some time the values come to under 30 or so.

My setup seems to show AQI values like 15, 25, etc in a room without any cleaning of course. how do i know the value is correct? It is my first time with this sensor so i am using the code from that link there directly (setting country to 2). On the website aqi.in it says 200+ in the area (outside)

Please guide!

Regards
Rajdeep Rath

The DSM501 has no factory calibration so there is no real baseline for the readings. It also has no fan, therefore the volume of air it samples is inconsistent. It would be difficult to calibrate without some sort of lab setup to produce air samples of a set AQI.

While the DSM501 sensors are great, they are generally used to give an indicative air quality measurement, rather than produce reliable quantitative data on an exact AQI. Perhaps something along the lines of a Plantower PMS5003 would be better suited to your application if you need to have more reliable data.

That said, a quick test would be to have the DSM501 next to a source of poor air quality such as a smokey candle, then put the device next to a clean air source such as an output of a HEPA filter. It will at least indicate that that device is doing it's job.

-Brian

Hello Brian,

Thank you for the detailed write-up. I can confirm that the sensor does work in the sense that if I get it close to smoke or bad air it does detect with the code I have used.

Regarding what you wrote - It also has no fan, therefore the volume of air it samples is inconsistent.

Can you tell me the purpose of the fan and how it would be positioned, if I were to add it to the apparatus myself? If you can provide some guidance it will be great and I can improve the sampling accuracy.

Regards
Rajdeep Rath

You can make an AQI.

The trick is the I or Index.

I created my index by finding the time of the year that offers the best Air Quality as measured by the local weather stations. Those weather stations guard their index values with their lives.

Once you got the day you will make the index, decided on the number of readings. I took 50 readings between the time of 0200 and 0300 on a day in May. Add those readings together and divide by the number of readings to get your index. Lets say your reading is 100.

100 would be the best Air Quality you measured. The 100 becomes your base line of best quality. This will take some code on your part. When you get a reading of 125 that is 25 points or 25% above your indexed value so your AIQ becomes 25%. A reading of 200 and your AIQ becomes 100%, which is very bad air quality as its 100% worse then the best reading.

Thank you for responding on this.i understand what you are saying. But going by Brian's writing can you explain to me :

Can you tell me the purpose of the fan and how it would be positioned, if I were to add it to the apparatus myself? If you can provide some guidance it will be great and I can improve the sampling accuracy.

I monitor the AQ outside my house by using a gas resistance sensor.

I monitor the AQ inside the house with a WaveShare Dust Sensor Module.

Outside the sensor is exposed to the weather by being in a Stevenson's shield.

Inside the sensor is exposed to the environment through a few holes in the case. My residence has a HVAC system that turns on a fan to blow hot or cold air around. I figure the fan as previously mentioned is for air circulation. I think it will be up to you if you want to add a fan and how that fan is added into your system.