A portable electronic system for in-situ measurements of oil concentration in MetalWorking fluids

摘要

MetalWorking Fluids (MWFs) are widely used to cool and lubricate machines andtools. By far, the most common MWFs are oil-in-water emulsions with oilconcentration (C oil) in the range from 1% to 10%, depending on type of oil,material to be worked, etc. In order to optimize emulsion and machineperformance, as well as for good waste policy, the right value of C oil shouldbe kept (approximately) constant during the MWF's lifecycle to compensateinevitable changes due to water evaporation, bacterial attack, oil adhesion tometal parts, etc.. This, however, requires periodic measurements, often skippedbecause they require unhandy operations and produce inaccurate results. In thiscontext, a new system is presented that is based on the falling ball principle,normally used for viscosity measurements, shown to be suitable also foraccurate C oil measurements. In our system, the transit time of the spherewithin the instrument is determined by means of inductive proximity sensors, aPT100 sensor is used for temperature whose effects on C oil are accounted forby means of an ad-hoc algorithm. A battery-operated electronic board has beendesigned that allows rapid and user-friendly " in-situ " measurements and aprototype of an whole portable and automatic instrument, suitable for in-situmeasurements, has been fabricated.