Pyranometer irradiance adjustment is flawed #60
Assignees
Labels
Comments
csatt
added a commit
that referenced
this issue
May 18, 2019
Replace the hardcoded irradiance adjustment with a configurable polynomial calibration. Polynomial curve: y = Ax2 + Bx x: temperature-scaled photodiode millivolts A: PYRANO_CAL_A (W/m2/mV2) B: PYRANO_CAL (W/m2/mV) y: irradiance If A is 0, scaling is linear. Intercept is always zero. The default value for PYRANO_CAL_A is 0.0, so the scaling is linear. The GUI doesn't support setting PYRANO_CAL_A in the calibration dialog, so the only way to change its value is by manually editting the config file. The GUI calibration dialog is the same as before, but the code does take into account non-zero values of PYRANO_CAL_A such that when the user enters the measured irradiance, that will be the irradiance after the calibration. This change also adds the photodiode temperature coefficent to the config file, so the user can change it. This is also not supported by the pyranometer calibration dialog, so it needs to be done by manually editting the config file. The default value for this coefficient was changed from 0.124 to 0.16.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
The current code has a hardcoded "adjustment" for an empirically observed error in the photodiode sensitivity where it reads slightly low at higher irradiances and slightly high at lower irradiances. This adjustment is flawed. The adjustment was much too large at very low irradiances.
A better way to deal with this phenomenon is to make the scaling polynomial rather than linear.
It also should not be hardcoded. The user should have the ability to tune the scaling including making it linear without any adjustment for this phenomenon.
The text was updated successfully, but these errors were encountered: