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Title: PAR comparison 12-2018
Date:2018-12-11
Data File: PARcompare_20181211.csv
Refers to:161073,10162,010161,030381,030380,LQ1570

We set up 5 PAR sensors from the lab (test sensors) next to each other for a comparison with an Ameriflux-calibrated (reference) PAR sensor from 2018-12-08 to 2018-12-11. The 6 sensors were set up about 0.5m outside of a south-facing lab window on the 2nd floor. There seems to be greater hysteresis in this comparison than the previous comparison in late September.

The sensors were connected to a CR6, which scanned the sensors every 10 seconds and recorded 10-minute averages. The line quantum sensor seems to be dead.

The new calibration coefficients are below.

Sensor model Serial number Factory calibration [µV/(µmol/m2·s)] New calibration [µV/(µmol/m2·s)] Recommendation
Kipp & Zonen PQS1 sn 161073 4.78 n/a (Calibrated by Ameriflux 08/2017) n/a
Kipp & Zonen PAR-LITE sn 10162 5.27 5.56 Apply new correction
Kipp & Zonen PAR-LITE sn  01061 5.27 5.16 Apply new correction
Kipp & Zonen PAR-LITE sn 030381 5.32 5.30 Apply new correction
Kipp & Zonen PAR-LITE sn 030380 5.31 2.91 This sensor needs to be checked
Licor Line Quantum sn LQ1570 ? n/a Sensor likely dead

 

Figure 1. Time series of PAR data. The max PAR in early December (~1500 umol/m2/s) is much lower than the max PAR in late September (~2500 umol/m2/s).

Figure 3. Example of hysteresis in the morning.

Regression Data

Residuals

Figure 2. Scatter plot of test sensor mV readings against the Ameriflux sensor umol/m2/s readings. Only values >0.2 umol/m2*s are included to prevent too much weight from night-time data. I used the slope of the linear regression lines to calculate the new calibration coefficients.