How is PM calculated from the raw data to the final data?
For example, I have three different PM10 readings for the same exact data and time. I understand that some of the PM10 calculations may be proprietary, but I would appreciate any documentation that would explain the differences between these values that should all represent the same measurement (i.e., PM10).
RAW
opc_pm10: 3.25
pm10_env: 15.667
FINAL
pm10: 62.913
Hi @joey.bail ,
Have you seen our technical note that describes how PM is calculated? It can be found as QAN-001 here.
Additionally, the opc_pm10 value is the raw value provided by the manufacturer of the underlying OPC and pm10_env is the raw PM10 value provided by the manufacturer of the nephelometer. For more information on why these values differ, I recommend taking a look at this paper or asking any questions here and I can answer them.
Thanks for your reply @dhhagan! I see the calculation for PM. It seems to me the final PM value references only the raw OPC PM values (i.e. MMj in Eq. 1), and not the nephelometer’s PM value. This makes sense to me based on the diameters that the nephelometer struggles to measure according to Figure 1.
The challenge I still have is deriving the final PM values from the raw OPC data. I have a large collection of raw data in .csv format for the past couple years without the final values. I could try to write a processing code that would convert the OPC’s raw PM values into final values using Eq 1, but I am curious-- Is there code already available that would allow me to do this, so I do not have to write this “conversion code” from scratch?
Hi @joey.bail , MMj accounts for the signal from the nephelometer.
If you’re just looking to get data converted, please reach out to support via the in-app chat in the lower right of your screen, and we’ll be sure to get that done for you.