Measuring small currents induced in coaxial cable - employs sinusoidal current of same frequency to simulate induced current using oscillator combined with amplifier

摘要

A coaxial cable subjected to vibration generates electrostatic between the conductor and dielectric material. These effects are measured by using analogy techniques whereby a sinusoidal current of the same frequency simulate the induced current. A coaxial cable (16) fixed between two fixed points (22) is subjected to vibration from an eccentric cam (20) whose speed is adjustable to induce a sinusoidal parasitic current in the cable. These currents are passed via a switch (14) to a directly coupled amplifier (10) with feedback circuits. The amplifier output is recorded (32) for examination. The switch is operated to alternate the amplifier input between the coaxial cable and a current simulator circuit (18). This simulator comprises an oscillator (38) followed by an amplifier (36) whose gain is adjusted by a potentiometer (42). A second amplifier (40) determines the current value.