Stainless steel capacitive pressure sensor for hostile environments: Sample-to-sample variability and reliability characterization

Assembly-type stainless steel (SS) pressure sensors are promising low-cost devices for high-pressure, corrosive-media applications. This report studies media compatibility, sample-to-sample variance, and reliability testing, as a step toward validating commercial viability of the technology. The sensor is realized from four main elements: a SS diaphragm die, a SS press plate, a tungsten carbide (WC) backing plate and a commercial off-the-shelf (COTS) SS vacuum coupling radiation (VCR) pipe fitting that also serves as the package. Media compatibility tests with nitrogen gas, deionized (DI) water, 45% wt. potassium hydroxide (KOH) solution, and 10% wt. sodium chloride (NaCl) solution at pressures up to 1,000 psi showed a repeatability error as low as 0.7% full-scale (FS). Sample-to-sample variance for three dimensionally identical packaged sensors was determined to be 9% FS. The reliability tests have been encouraging, with a single packaged sensor tested for over 1 million cycles to date in nitrogen gas with a repeatability error of 6% FS.