HV alarm device for construction workers - uses semiconductor field detector coupled to fail=safe audible warning unit

摘要

The high-voltage detector comprises a flat probe (20) constructed from a flat circular foil of flexible material (21) on both sides of which are conductive or semiconducting layers (22, 23). Connecting lugs (24, 25) are attached to the foil before the layers are deposited. The probe is intended for universal use and may be attached to the clothing of construction workers, for example. The probe is connected to an amplifier and the voltage proportional to the electric field generated by the high voltage, is amplified and detected. The demodulated voltage controls a multivibrator. This in turn drives an audible warning device. As the warning device is battery-operated, an auxiliary circuit provides a continuous alarm signal if the battery power is below a safe level.