Technique and apparatus for measuring a direct current flowing through a

Abstract

A technique and circuit for measuring direct current flowing through a conductor at a high voltage employs a capacitor connected in series with the conductor, and a neon lamp connected in parallel with the capacitor. The series connected capacitor and conductor are connected to a high voltage source such that the current flowing through the series connected capacitor and conductor charges up the capacitor. Since the capacitor and the neon lamp are connected in parallel, the voltage across the electrodes of the neon lamp follows the voltage across the capacitor. When the voltage across the electrodes of the neon lamp reaches the lamp's ignition voltage, the neon lamp fires, and discharges the capacitor until the voltage across the electrodes of the neon lamp falls to the lamp's extinction voltage. The light signal generated by the neon lamp is picked up by a fiber optic cable and transmitted to a remote receiver for processing. The direct current flowing through the conductor may then be calculated by the remote receiver from the frequency of the transmitted light signal, or a qualitative indication of the current may be made through visual observation of the lamp's intensity.