Microcomponents of an interferometric pressure sensor module
Optical measurement principles often offer advantages over electrical sensors. For this reason, interferometric evaluations of membrane bending are also increasingly finding their way into pressure sensor technology. However, fiber-optic light transmission and complex evaluation units make today’s solutions price-intensive, so they are usually reserved for special applications.
Using MEMS wafer technologies and a silicon photodiode array with embedded laser light source (naked VCSEL), the CiS Research Institute has succeeded in integrating the complete optical sensing of the pressure-sensitive, membrane (Silizum) in a very flat package space – comparable to capacitive or piezoresistive sensors.
The 500 μm thin interferometer chip is suitable for measuring membrane deflections of more than 100 μm and provides sinusoidal signals with a period of 375 nm, which allow resolutions in the nanometer range by interpolation. In conjunction with silicon transducer cores, a functional model was realized for a pressure sensor module for absolute pressure measurement for a measuring range of 0-10 bar. A particular advantage of the measurement principle is that membranes made of other reflective materials can also be scanned in such a module.
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