Be very careful with this. It does work and is accurate enough for hobbiest work.

Covers theory, tips, pratical advice, sources, parts, links to other sites, and information about HV probes uses and design.

and Multimeter, Outokumpu Technology, Carpco Division

A fairly accurate safe way to measure really high voltages.

How to measure that HV with some precision.

Manufactures hipot testers for both AC and DC measurements including a complete ground safety, fault locating, and measurement systems.