High Voltage Technique: The high voltage, or porosity technique, can be used to test coatings up to 25mm (1”) thick and is ideal for inspecting pipelines and other protective coatings. Coatings on concrete can also be tested using this method.
A power supply generates a high voltage DC to a probe. As the probe passes over a flaw, a spark at the contact point sets off the alarm.
Continuous DC holiday detectors, such as the Elcometer 236 Holiday Detector, require direct connection to the conductive substrate. The Elcometer 236 holiday tester provides the user with complete control of voltage and sensitivity settings and is available in 2 versions- 15kV and 30kV.
For more information, see the Elcometer Guide to Pinhole & Porosity.