EEMCS

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Official URL: http://dx.doi.org/10.1016/S0924-4247(99)00188-0

Abstract

The micromechanical equivalent of a differential pressure flow-sensor, well known in macro mechanics, is discussed. Two separate pressure sensors are used for the device, enabling to measure both, pressure as well as volume flow-rate. An integrated sensor with capacitive read-out as well as a hybrid, piezo-resistive variant is made. The fabrication processes are described, using silicon and glass processing techniques. Based on the sensor layout, equations are derived to describe the sensor behavior both statically as well as dynamically. With the derived equations, the working range of the sensor and the thermal and time stability is estimated. The computed results of the stationary behavior are verified with the measured data. A good similarity in linearity of the pressure/flow relation is found. The computed hydraulic resistance, however, differs from the measured value for water with 21%. This difference can be explained by the high sensitivity of the resistance to the resistor channel cross-section parameter in combination with the difference between the rounded etched shape and the rectangular approximation. From fluid dynamics simulations, a working range bandwidth of about 1 kHz is expected. Thermal influences on the sensor signal due to viscosity changes are in the order of 2% flow signal variation per Kelvin. From these results, it can be concluded that the sensor can be used as a low cost, low power consuming flow and pressure-sensing device, for clean fluids without particles and without the tendency to coat the channel walls. If a high accuracy is wanted, an accurate temperature sensing or controlling system is needed.

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