The SOI sensor will mostly be used in extrusion facilities in plastic processing. The process depends on filling moulds completely with the plastic raw material. This is where the SOI comes in: It measures pressure precisely and notifies the system immediately when the injected plastic reaches a certain point. SOI stands for Silicon-on-Insulator and refers to a sensor encased in a layer of silicon dioxide for complete electrical insulation. The outer SOL (Silicon-Over-Layer) on top of that layer includes independent piezoresistors in the silicon membrane. Traditional MEMS pressure sensors use the layer between the positive and negative doping – the so-called p-n transition – as insulation, allowing a current to pass in one direction only. MEMS is an acronym for Micro-Electro-Mechanical Systems and refers to miniature components that process mechanical and electrical information. By stark contrast to SOI sensors, MEMS sensors can only be used at temperatures up to around 125° centigrade.
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