I've bought a Teraohm meter with a rather high test voltage of 500 V.
Quite a specialized piece of kit, but i need it to test my homemade SMU Triax cables: cables from Keithley have a resistance of 10^15
between the two inner conductors, and that has to be measured at 500 V.
My test cable reached something like 5x10^13
, so it's only 20 times worse than the cables from the manufacturer (but i didn't have to pay 400 bucks per cable). I don't think that i'll reach the manufacturer specs with my cables, turns out that black heat shrink tubing is way more conductive than i'd like it to be for this job.