Impedance Measurement of Rolling Bearings Using an unbalanced AC Wheatstone Bridge

TL;DR

This paper explores using an unbalanced AC Wheatstone bridge to measure the electrical impedance of rolling bearings, enabling reliable condition monitoring in industrial applications.

Contribution

It introduces the AC Wheatstone bridge as a novel, effective method for impedance measurement of bearings with low phase angles at kHz sampling rates.

Findings

The AC Wheatstone bridge effectively measures impedance in rolling bearings.

Simulation and uncertainty analysis validate the method's reliability.

Sample measurements demonstrate practical applicability in bearing condition monitoring.

Abstract

Industry 4.0 drives the demand for cost-efficient and reliable process data and condition monitoring. Therefore, visualizing the state of tribological contacts becomes important, as they are regularly found in the center of many applications. Utilizing rolling element bearings as sensors and monitoring their health by the electrical impedance method are promising approaches as it allows e.g. load sensing and detection of bearing failures. The impedance cannot be measured directly, but there are various methods available. This work discusses advantages and disadvantages and suggests the AC Wheatstone bridge as a reliable way of measuring impedances with low phase angles at sampling rates in the kHz range. The corresponding equations are introduced, a simulation built, an uncertainty mode and effects analysis carried out and sample measurement results of real rolling elements shown. It can be demonstrated that the AC Wheatstone bridge meets the proposed requirements for sensory utilization and condition monitoring when the bearing is operated in the hydrodynamic regime.