What Does Holiday Detector, High Voltage Mean?
Holiday detector, high-voltage is an instrument that uses high voltage (greater than 800 volts) electricity to discover discontinuities in thicker non-conducting or insulating film (between 500 microns (20 mils) and 25mm (1") thick) that is applied over conductive substrates. Insulators include some paints, varnishes and other coatings that are poor electrical conductors.
The voltage used is determined by the coating's type and thickness. A high-voltage holiday detector can be destructive because the high voltage pulses used to detect holidays can burn or destroy some of the thinly coated areas.
Holiday detector, high voltage type is also known as a spark tester because of the spark it gives off whenever a holiday or coating discontinuity is found.
Corrosionpedia Explains Holiday Detector, High Voltage
Holiday detector, high-voltage, is an instrument used to check for discontinuities in coatings thicker than 500 microns (20 mils). It typically consists of a power source, a ground wire, a probing electrode and an indicator. The indicator is a light or sound that is triggered when a holiday is detected.
There are two types of high-voltage holiday detectors available: the pulsating direct current or the continuous direct current. The pulsating direct current holiday detector is the most commonly used type.
A pulsed direct current holiday detector discharges an adjustable and regulated 'pulsed' or “cycling type” of high voltage. It is suitable for use in dirty, damp, contaminated or slightly conductive coating surfaces.
A continuous direct current holiday detector discharges high voltage continuously and is suitable for holiday testing non-conductive coatings on pipelines, storage tanks and valves.