AirGradient Forum

PM2.5 Calibration Formula

Components
#1

Hi, I have just received a fully assembled Airgradient One. But I am confused by the PM2.5 Calibration Formula page in the advanced settings. What should I select if I have a fully assembled unit that comes with a test report?

I see PMS5003_20240826 was preselected, and I found in the notes section (pasted below), that the values in the test report was set initially, but changed to PMS5003_20240826 minutes later. My guess would be that was when I clicked the apply calibration button from the banner message (screenshot attached below) right after I set up my device.

id,title,description,date,measure,location_id,place_id
"32270","Calibration formula change","The calibration formula has changed, now slr_PMS5003_20240826 is applied","2025-12-04T08:38:01","pm02","178334","20263"
"32239","Calibration parameter change","The calibration parameters have changed, now offset -0.271 / scaling factor 0.014 epa false are used","2025-12-04T08:33:26","pm02","178334","20263"
"32238","Calibration parameter change","The calibration parameters have changed, now offset -0.271 / scaling factor 0.014 epa false are used","2025-12-04T08:33:26","pm02","178334","20263"
"32237","Calibration formula change","The calibration formula has changed, now custom is applied","2025-12-04T08:33:26","pm02","178334","20263"
"32236","Calibration formula change","The calibration formula has changed, now custom is applied","2025-12-04T08:33:26","pm02","178334","20263"

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image3180×670 126 KB

Also, assuming we should use the value from the test report for the calibration page, if a user buys a fully assembled unit, I think the message asking the user to apply the calibration should not appear or should apply the value from the test report, do you agree?

Side note, I think the time in my notes were wrong, it should have been 8PM not 8AM.

#2

Hi @superjeng1! Thanks for bringing this up. Yes, you’re totally right - with the test report V2 each unit is now individually calibrated with a reference so you no longer need to apply the batch correction formula. I am creating a ticket for the team to remove the banner suggesting application of the batch calibration formulas. Thanks a lot, again, for bringing this up!

#3

Hi @Altair_AirGradient! Thanks for your reply. So I should set “PM2.5 Calibration Formula” to “Custom via PM Count”, then set the “Scaling Factor” and “Offset” according to my test report, but keep “Apply EPA Formula” unticked, is that correct?

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image1920×967 142 KB

Also, one bug I think I found is that, when changing the calibration settings, the notes that were automatically add had the wrong timestamp. In my case, it was 8PM but the note said 8AM.

#4

Yes, that is correct!

The EPA correction aims to align (classic) Plantowers sensor with ambient reference measurements. As we already align our measurements with a reference now with Test Report V2, there is no need for EPA anymore.

Regarding the timestamp bug, I will have a look and create another ticket for the dev team - appreciate your diligence!

#5

Thanks @Altair_AirGradient! I will check the EPA formula checkbox.

I am curious what is the difference between “Custom via PM2.5 Raw” and “Custom via PM Count”?

I see “Calibration Parameters via Count” in the test report so that’s why I assumed we should use “Custom via PM Count” so correct me if I am wrong.

On a side tangent, for temperature and humidity, I assume we should select raw data, as I don’t see any calibration for them in the test report, is that also correct?