High Throughput Wear Debris Detection in Lubricants Using a Resonance Frequency Division Multiplexed Sensor

With a long time goal of detecting signs of potential machine failure, we demonstrate a proof-of-principle multiplexed, multichannel, inductive pulse sensor based on resonant frequency division multiplexing for high throughput detection of micro-scale metallic debris in lubricants. In the four-channel sensor, each sensing coil is connected to a specific external capacitance to form a parallel LC circuit that has a unique resonant frequency. Only one combined sinusoidal excitation signal consisting of four frequencies components that are close to the 4 sensing channels' resonant frequencies was applied to the sensor, and only one combined voltage response was measured. Because each sensing channel exhibited a peak amplitude at its resonant frequency, the signals for each individual channel were recovered from the combined response by taking the spectrum components at each resonant frequency with an improved signal-to-noise ratio. Inductance change for each channel was then calculated from signals of individual channels. Testing results show that the use of resonant frequency division multiplexing allows simultaneous detection of debris in lubricants using only one set of detection electronics; for the four-channel sensor, there is a 300 % increase in throughput. The resonant frequency division multiplexing concept can be potentially applied to a multichannel oil debris sensor with a large number of sensing channels to achieve a very high throughput, which is necessary for online health monitoring of rotating and reciprocal mechanical components.