As I understand it the guard ring is supposed to stop radiation and leakage currents from influencing the plate (antenna) readings since it carries low voltages, something like a Faraday cage along one plane.

 

I think your understanding of the guard ring is pretty good.

The one I made was by milling a blank printed circuit board. The was a large copper disc in the middle surrounded by a narrow guard ring. Other conductive objects near the pickup plate and the device being tested would affect the electric field reading. If your pickup plates are arranged on the same plane and you have guard rings then once calibrated I doubt you would have to worry about interaction.

Please explain what you mean by "...but most of our dielectrics are metal with an infinite constant..."

Dielectrics are insulators, otherwise they can't hold a charge. Can you explain the physical arrangement of the thing you are measuring and what is between it and the pickup plate?

 

Please explain what you mean by "...but most of our dielectrics are metal with an infinite constant..."

Dielectrics are insulators, otherwise they can't hold a charge. Can you explain the physical arrangement of the thing you are measuring and what is between it and the pickup plate?

Right, I'm confused about how to predict the current that would flow in a conductor then. Metals, lets say copper, have an infinite dielectric constant because they're conductors so in the equation for current due to changing flux in an isotropic material what value are we supposed to use or is there a different derivation for conductors? https://en.wikipedia.org/wiki/Displacement_current#Isotropic_dielectric_case

 

Dielectrics are insulators, otherwise they can't hold a charge. Can you explain the physical arrangement of the thing you are measuring and what is between it and the pickup plate?

A coil with a changing current that produces a magnetic and electric field is the source and between that and the plate is air.

 

Woops, the displacement current occurs in the dielectric which is in this case air and its constant is 1.0006. The displacement current is equal to the conduction current in magnitude.

Very silly misunderstanding!