Hello I have the display shown below,two questions:
1.how can I see the Y axes is voltage?
2.i was given an example where 0.5V, with ρ = 0, at Zo
what is the mathematical logic for translating 0.5V to ρ = 0?
3.How do we practicaaly in lab calculate the velocity factor of a signal going threw PCB?

 

To understand the display you will need to understand and be aware of the controls settings. We do not see that information in your post.
AND, unfortunately, I have no "mind reading " ability AT ALL!!