AD Power Co.
- Products include standby power meters (such as Wattman HPM-100), oscilloscopes, spectrum analyzers, DC power supplies and other instruments.
- http://www.adpower21.com/eng/

Rectifiers and Electronics
- Manufacturers of AC/DC high voltage and high current testing equipments, spark testers, industrial voltage stabilizers, AC and DC welding equipment, battery chargers. New Delhi, India.
- http://www.testingequipments.in

Sphere Gap Breakdown Voltage Tables
- How to measure high voltages with some precision.
- http://home.earthlink.net/~jimlux/hv/spherev.htm

Measuring High Voltages by Spark Length
- Table and graph gives maximum spark length for DC or low frequency sinusoidal voltages. A fairly accurate safe way to measure really high voltages.
- http://www.kronjaeger.com/hv/hv/msr/spk/index.html

Electronic High Voltage Meters
- Circuit and formula for constructing high voltage probes.
- http://www.kronjaeger.com/hv/hv/msr/elc/

Vitrek
- Manufactures high potential testers for both AC and DC measurements including a complete ground safety, fault locating, and measurement systems.
- http://www.trirep.com/vitrek.htm

Basics of High Voltage Probe Design
- Covers theory, tips, pratical advice, sources, parts, links to other sites, and information about HV probes uses and design.
- http://www.repairfaq.org/sam/hvprobe.htm