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This paper describes a microdischarge-based pressure sensor for harsh liquid environments that utilizes a ceramic package sealed with a deflecting diaphragm that also serves as a cathode. Located within the package is a reference cathode and an anode. The microdischarges are created between the two cathodes and the anode. The external pressure deflects the diaphragm, varying the interelectrode spacing and changing the differential current between the two competing cathodes. The electrodes are fabricated from a Ni foil and separated by dielectric spacers within a micromachined glass cavity. The structures are enclosed within a 1.6-mm3 ceramic surface mount package. Device sensitivity is approximately 4900 ppm/ lbf/in2 (72 000 ppm/atm), and diaphragm displacement is approximately 0.15 μm/atm.