Improving sensitivity of an inductive pulse sensor for detection of metallic wear debris in lubricants using parallel LC resonance method

Abstract

Detection of small metallic wear debris is critical to identify abnormal wear conditions for prognosis of pending machinery failure. In this paper we applied an inductance–capacitance (LC) resonance method to an inductive pulse debris sensor to increase the sensitivity. By adding an external capacitor to the sensing coil of the sensor, a parallel LC resonance circuit is formed that has a unique resonant frequency. At an excitation frequency close to the resonant frequency, impedance change (and thus change in voltage output) of the LC circuit caused by the passage of a debris particle is amplified due to sharp change in impedance at the resonant peak; thus signal-to-noise ratio and sensitivity are significantly improved. Using an optimized measurement circuit, iron particles ranging from 32 to 96 µm and copper particles ranging from 75 to 172 µm were tested. Results showed that the parallel LC resonance method is capable of detecting a 20 µm iron particle and a 55 µm copper particle while detection limits for the non-resonance method are 45 and 125 µm, respectively. In contrast to the non-resonant method, the sensitivity of the resonance method has been significantly improved.

An Inductive Sensor for Real-Time Measurement of Plantar Normal and Shear Forces Distribution

“…Inductance change for each sensing coil can, therefore, be calculated from individual signals. More details about resonant frequency division multiplexing techniques can be found in [19] and [20]. From the measured inductance changes, foot forces can be back calculated from calibration curves.…”

Research on the Influence of Excitation Frequency on the Sensitivity in Metal Debris Detection with Inductor Sensor

“…The short-circuit loop resistance 4 of the ferromagnetic debris can be calculated with formula (8) and formula (9). So the changing rate of the microsensor coil inductance can be described as formula (15) while it detects ferromagnetic debris. Consider the following:…”

“…The constant parameters in (15) can be substituted with undetermined coefficients. Here substitutes for 2 2 4 , substitutes for 4 2 1 , substitutes for 1 /(2.5 × 10 7 ln 2 ( / )), and substitutes for ( 3 − 1 )/ 1 .…”

“…The changing rate of the sensor inductance is about 0.04%. About 32 m iron particle was detected in experiment with the LC resonance method; however, the copper particles which can be detected in experiments are also fairly large about 75 m with 2.8 MHz excitation frequency [15]. Liu et al [16,17] built a simulation model of detecting metal debris by the microinductor sensor with Ansoft software.…”

Improvement of Sensitivity and Detectability of the Three-Coil Wear Debris Detection Sensor Using LC Resonance Method and Modified Lock-in Amplifier

“…Besides that the sensors with different coil shapes were also studied which mainly includes planar coil structure and spiral coil structure [2,9,10] . The second important research direction is that sensors with micro channel structure which outstanding characteristic is that the inner diameter of the channel is often smaller than 1mm [11][12][13][14] but have high sensitivity. Generally this kind of sensor can successfully detect up to 20um ferromagnetic particles and 55um non-ferromagnetic particles, but because of the limitation of its maximum flow rate, it is difficult to meet the requirements of the large flow engineering.…”