When using high voltage DC holiday detectors on concrete, which type is recommended?

High voltage DC holiday detectors are specifically designed for the detection of coating defects, such as pinholes or holidays, on substrates like concrete. The recommended type is high voltage DC constant current. This choice is ideal because it ensures a steady current flow through the test area, allowing for reliable identification of flaws in the coating system.

Using constant current assists in providing a uniform sensitivity and consistent testing results, which is crucial for accurate defect detection. It maintains a steadiness in the electrical output, minimizing the risks of false indications that can occur with pulsed or fluctuating voltage types.

In contrast, high voltage AC, whether pulsed or constant voltage, can introduce complexities in interpretation and may not provide the necessary sensitivity for concrete substrate testing. AC systems can also potentially generate capacitive coupling effects, which may lead to misleading results. Therefore, for optimal performance in detecting holidays on concrete, a high voltage DC constant current detector is the most effective and trusted choice.