There has been various efforts in the past to develop contamination sensors that can be mounted on machinery and in fluid power systems to continuously monitor contaminants in hydraulic fluids, fuels or lubricants. Some of these known designs use the concept of light extinction. This concept is related to the concept of light scattering. A beam of light is directed through the fluid and its intensity is monitored by a photodetector, located on the other side of the flow channel. The amount of light that gets through the fluid is measured and compared to the amount that was originally delivered from the source. The difference between the originally delivered light energy and the energy measured on the other side of the flow channel is the amount of light energy extinct. This amount of light energy is either absorbed by the fluid, absorbed by the contamination or scattered by contaminants in the fluid. The amount of light extinct is a measurement of the level (type, size and amount) of contaminants in the fluid. In various systems using light extinction, the light is directed through the fluid and by the use of a mirror the light is reflected back through the fluid to the photodetector. Other known designs use the concept of light scattering. This concept is also based on directing a beam of light through a fluid. However, light scattering sensors use the amount of light scattered as indication for the level of contaminants in the fluid. Detection of foreign matter (contaminants) in liquids through the light extinction or the light scattering concept are related. An energy balance reveals that the light energy extinct in a beam is composed out of all the light energy scattered in all directions (except into the direction of the light beam monitoring photo detector), the amount of light absorbed by the fluid (for a constant flow channel dimension this is a constant) and the amount of light energy absorbed by the contamination in the light beam. The contaminants might be solid particles, like sand or metal particles; droplets of immiscible fluids in the background fluid, like water droplets in oil or gas bubbles in the background fluid; and/or like air bubbles in a foaming lubricant. The photodetectors converts the light signals into electrical signals in response to the scattered light or the extinct light. The signals are in the form of light burst which are converted into electric pulses by the photodetector. The height of the pulses is a measurement of particle (droplet, bubble) size. Currently existing contamination sensors are too expensive to be placed in machines and/or fluid power system for reliable detection of different types and levels of contaminants; such as, solid particles, water droplets and air/gas bubbles.
The present invention is directed to overcoming one or more of the problems as set forth above.