| abstract |
(57) [Summary] The first capacitive pressure sensor (70A, B) has a single crystal structure (sapphire with a cavity) bonded by fusion. The second (70A, B) has an elongated and thick crystal structure. The third (70A, B) utilizes the electric field emanating from the back of the capacitor electrode. The first differential pressure transmitter uses a process barrier (71) and longitudinal members as sensors (70A, B). The second differential pressure transmitter uses a single crystal structure having a stress separating member as a sensor (70A, B). Basically, a capacitive sapphire sensor with a thick slab-like cavity is directly exposed to the process fluid. The slab is 15 × 3 × 2 cubic mm, the cross section of the cavity is 1 mm × 0.5 μm, and the capacitance is 42 pF. |