my account PosiTest HHD (High Voltage Holiday Detector)
What is a holiday detector?
A holiday detector is a non-destructive instrument for detecting discontinuities in a coating system including holidays, pinholes, and cracks. Other names include porosity detector, continuity tester, and holiday tester.
There are two types of pinhole detectors: low voltage (wet sponge) and high voltage (spark tester). Low voltage detectors, like the PosiTest LPD, are typically used on coating systems less than 500 µm (20 mils) thick. High voltage spark testers, like the PosiTest HHD operate at voltages up to 35,000V and are typically used on coatings more than 500 µm (20 mils) thick.
How is a high-voltage test performed?
A high-voltage holiday test is performed by moving a charged electrode over the coated surface. When a holiday is encountered, current flows from the electrode into the substrate. The current returns to the detector through the ground (earth) wire, completing the circuit and triggering audible and visible alarms. An integrated peak reading voltmeter measures and displays the output voltages on the display while in use.
How does the PosiTest HHD measure coatings on concrete?
When measuring coating thickness, concrete is not considered a 'conductive' substrate, as it is much less conductive than metal. However, concrete is still slightly conductive, and can carry enough current to allow holiday detectors to function. Therefore, for the purposes of holiday detection, concrete is considered a 'conductive' substrate.
What is meant by the term 'stick type' or 'wand' holiday detector?
A 'stick type' holiday detector is a standalone detector with internal battery power and electrodes that attach to the end of an electrode rod (stick). 'Wand' or 'Belt-style' detectors typically have a separate battery pack carried on the belt or shoulder strap and electrodes that attach to a handheld wand. The PosiTest HHD is the first combination stick type/wand type instrument on the market. With the optional handheld wand accessory, the PosiTest HHD converts into a wand style instrument suitable for voltages less than 15k.
Why is porosity measurement important?
After a protective coating has been applied, it is important to ensure that there are no defects or discontinuities present that expose the substrate beneath. Small areas of thin or missing coating, called 'pinholes' or 'holidays', can become foci for corrosion and drastically reduce the life of a protective coating system. They can be invisible to the naked eye. Porosity detectors are often used in applications where corrosion is difficult to monitor, or in aggressive service environments where performance of the protective coating is critical.