Calibration

Many people have come up with calibration models to make the data output match popular units that are used in research and academia.  I have chosen to make my units report in micrograms per meter cubed (ug/m^3).

To do this I compared the output of the sensor’s ratio data with a Dusttrak II Model 8530 air sampler with a PM2.5 impactor attached.  I sampled the Dusttrak and my sensor at 1 minute intervals.

For my PM 2.5 (particulate matter 2.5 um) source I used matches and candle smoke.  Since smoke is one of  the major components that I am interested in this should provide my project with the best calibration.

The calibration curve I came up with is:

PM25= .1809 * (ratioP2)^2 + 3.8987 * ratioP2,    (+ 2.5003)

R^2=.9858 from a PM2.5 concentration of 0 up to 600 ug/m^3

I removed the 2.5003 from the regression because I wanted a zero ratio to read zero ug/m3.  It did not change the R^2 value much at all.

Here is my calibration file in excel

Keep in mind that my regression curve is different than other published curves because I changed the threshhold voltage by using a resistor across Pin 5 on the senor and reading off of P2 (pin 2) on the sensor instead of the P1 (pin 4).

 

Research referenced:

Laboratory Evaluation and Calibration of Three Low-Cost Particle Sensors for Particulate Matter Measurement – You have to pay for the full text or find a database you have access to that can get you the full copy.

Laboratory Evaluation of the Shinyei PPD42NS Low-Cost Particulate Matter Sensor – Free full text

 

 

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