Method for onsite measurement of common-mode voltage of conducted noise based on shoe-shaped wearable sensors

Abstract

This paper proposes a method for the onsite measurement of the common-mode voltage of conducted electromagnetic noise in data transmission cables without direct contact with the reference ground of the noise to be measured. The return path of the noise is a capacitive coupling between an electrode and the floor of the measurement site. The capacitive coupling is evaluated by applying a radio-frequency signal to an electrode facing the floor and measuring the amplitude at another electrode placed adjacent to the former electrode. These electrodes and measurement circuits are installed in the soles of shoe-shaped wearable sensors. Furthermore, instead of attaching a probe to a transmission cable, the maintenance engineer grasps the cable by hand. The noise in the cable passes through the capacitive coupling between the cable and the hand, through the human body, and through the capacitive coupling between the bottom electrode in the shoes and the floor. The noise voltage between the two electrodes in the sensor shoes is measured. The actual noise voltage and the measured voltage at various capacitive coupling levels and frequencies are recorded prior to the actual measurement at the site and their relationship is expressed by empirical formulas. The measurement system was evaluated at three typical office floors that had different floor structures. In all cases, the error between the actual noise voltage in the cable and the estimated voltage obtained by the proposed system was less than 1.33 dB. The results indicate that the proposed method can be used to quantitatively measure the common-mode voltage of conducted noise in a real-world environment.