Damjan Hajsek <hajsek.dam...@gmail.com> writes: > Anyone know what to use in > [StdCalibrate] > > [[Corrections]] > > to correct UV index? Because now at night it is UV = 15
(I don't have any actual experience here, either with weewx calibration or with UV sensors that ever show 15.) Typically, "calibration" involves minor adjustments to a sensor that is basically working ok, like adding 0.7 hPA to pressure. There is an underlying assumption that the sensor has the right slope but just a small offset. A UV sensor that reports a UV index of 15 at night sounds so seriously off that it seems more likely that something is catastrophically wrong which cannot reasonably be resolved with calibration. I have not checked calibration on my UV sensor, but it reliably shows 0 at night and patterns that appear to corrrelate well with sunny vs not and sun angle. I would not be shocked if it reads 3.8 when it should read 4.0; I would have to be far more thorough to figure that out, vs eyeballing graphs and not being suspicious. I would recommend looking at all other ways of observing the sensor value (console?), and see if there are any setup errors. Finally, I would log the data without calibration for a while, and graph that in a scatter plot against UV data from some nearby station that you believe is working ok. If that turns out to be a line with slope 1 and offset 15, then subtracting 15 is good strategy. But until you know that such a relationship holds, the assumption that there is a single linear offset seems unwarranted. Greg -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to weewx-user+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
