A simple high voltage probe was built using a clear acrylic Perspex tube (with an external diameter of 10mm and an internal diameter of 3mm) and a 3D printed handle and tip (red plastic on picture above). The probe has a ratio of 1:100000 which means that for a 100kV input it provides a 1V output. The output can be easily connected to an Arduino nano with a 1.2V internal reference. The details of he electronic circuit are provided below.
A high voltage input is connected to a 1:100000 voltage divider. The upper part's resistance is euqal to 1.410 GOhma and is rated 105kV. The lower part's resistance is equal to 1.410Kohma. The output is buffered using a voltage follower (TLC272).