Inductive Coulter counting: detection and differentiation of metal wear particles in lubricant

A device based on an inductive Coulter counting principle for detecting metal particles in lubrication oil is presented. The device detects the passage of ferrous and nonferrous particles by monitoring the inductance change in a coil. First, the sensing principle is demonstrated at the mesoscale using a solenoid. Next, a small planar coil suitable for use in a microscale device is tested. Static tests are conducted on the planar coil using iron and aluminum particles ranging from 80 to 500 mu m. The testing results show that the coil can be used to detect and distinguish ferrous and nonferrous metal particles in lubrication oil; such particles can be indicative of potential machine faults in rotating and reciprocating machinery. The design concept demonstrated here can be extended to a microfluidic device for real-time monitoring of ferrous and nonferrous wear debris particles.