Single pole voltage probe - uses liquid crystal displays and glow lamps to indicate voltage ranges

摘要

The single pole voltage probe has additional, independant, isolated branches of lower internal resistance lying in parallel with the main measuring circuit (L1-L4). Liquid crystal displays (L) and light emitting diodes or glow lamps (G) indicate the measured voltage ranges when their thresholds are exceeded. If the ground resistance (R5) is high the liquid crystals (L) indicate and the glow lamps light up if the ground resistance is low. The circuit can be housed in a ball point pen or in a screwdriver.