Measuring panel IV curves

There are several ways of measuring solar panel IV curves. I wanted to make such measurements to get a better feel for condition of panels and how exactly they react to things like shading and temperature changes.
I tried using a set of resistors to apply various load resistances then manually graph all the numbers. While this works, it is slow and laborious. Lighting conditions often change during the process (clouds going over, etc) which makes it hard to get smooth, relable data that way.
I found the following rather old article which had a clever technique involving charging a capacitor (see figure 3).


test setup

Test setup

Plotting the data:

I find it best to plot the data with Octave from *.csv files so that I can superimpose the power curves.

Notes:

Index