The highest voltage (kV) reading you will be able to get on a fenceline depends on which model charger you have.

One way to find that is to shut of the charger, remove the fence feed line, plug in the charger and take a reading right on the charger output post. That is the max you can generate with that charger.

All fences on one charger will read about the same number. There will also be some variation due to weather which you can minimize by putting your thumb on the ground stud (under the rubber cover) on the Gallagher tester.

If here is a large difference between the bare terminal voltage and the voltage after the fence wire is reconnected either you have  a short somewhere or a lot of damp weed pressure.

If you have the orange Gallagher fault finder/meter you can press the button and switch from reading voltage (kV) to amps and direction (A).

Start at the charger and hold the metal strip against the wire until a number and arrow show. This is measuring the amps and showing the direction of the flow.  Think of electricity in a fence like water flowing from a pump (the charger).

Water flowing in a hose has pressure (similar to kV) and flow (similar to Amps). the Gallagher meter will let you measure both.  If the kV (pressure) is low, you use the Amps reading (flow meter) to find the direction the water and electricity are flowing to the leak (short).

Weed pressure is like a soaker hose. A short is like a hole in a pipe. the meter helps find shorts.  Follow the fence wire from the charger to each junction and the Amp and arrow will tell you which directionn the flow/leak is and roughly how much flow there is. A flow of 1 to maybe 2 amps is likely due to weed pressure. A flow of 8-20+ amps is going to a short. 

My tester has allowed me to find a cracked insulator that I could not even see. The flow went to a corner that looked normal. As a last resort I changed the wire insulator and problem was fixed.

Good luck. I hope this helps.

Jim at Dawn