Ceramic MEMS designed for wireless pressure monitoring in the industrial environment
M. Pavlin, D. Belavič, F. Novak
Sensors, 2012, 12(1): 320-333
This paper presents a design of a wireless pressure-monitoring system for harsh-environment applications. Two types of ceramic pressure sensors made with a low-temperature cofired ceramic (LTCC) were considered. The first type is a piezoresistive pressure sensor. It is made with four thick-film resistors on a ceramic diaphragm. Each thick-film resistor acts as a strain gauge, which is capable of translating the strain into an electrical signal. The energy consumption depends mostly on the value of the resistance of thick-film resistors and on the operating voltage. The test samples have values for the power consumption over a very wide range – between 0.015 and 150 mW. The second type is a capacitive pressure sensor, which is based on changes of the capacitance values between two electrodes: one electrode is fixed and the other is movable. The displacement of the movable electrode depends on the applied pressure. The energy consumption of this type of pressure sensor depends mostly on the values of the operating frequency and the capacitance of the capacitor. The test samples have values for the power consumption of less than 0.2 µW. Low power consumption and reliable operation in the presence of disturbances, like electromagnetic interference, parasitic capacitances, etc., proved to be contradictory constraints. However, an acceptable solution using energy-harvesting techniques have been developed.
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