Optimized design and process for making a DC voltage reference based on MEMS
A micromechanical moving plate capacitor has been designed and fabricated for use as a dc voltage reference. The reference is based on the characteristic pull-in property of a capacitive microelectromechanical system (MEMS) component. The design is optimized for stability. A new silicon-on-insulator (SOI) process has been developed to manufacture the component. We also report on improved feedback electronics and the latest measurement results.
Voltage Sensing using MEMS Parallel-Plate Actuation
Microelectromechanical systems (MEMS) have been proposed as DC electrical metrology references. The design reported here is the first to enhance the qualities of a MEMS DC reference with potential tuning and sensing via an isolated and monolithically integrated MEMS technology and, thereby, convert a stable parallel-plate voltage reference to a simple, sensitive, low-burden voltage sensor. This on-chip system reliably measures unknown potentials ranging from -60 V to 60 V with sampling times less than 10 msec. In the initial design, the system is used to measure atto-amp leakage current though 10 P!, suspended, MEMS isolation.
HYPERGOLIC REACTION MECHANISMS OF CATALYTICALLY PROMOTED FUELS WITH ROCKET GRADE HYDROGEN PEROXIDE
Abstract The coupling of the physical and chemical processes controlling the ignition delays (τ ign ) of hypergolic propellants complicates the direct analysis of the transient ignition processes. The transport properties of both the propellants and the ambient gas, and the heat of vaporization and reaction affect τ ign and must be considered experimentally. Furthermore, since hypergolic ignition occurs, by definition, on contact, the mechanics of initial contact and subsequent mixing can affect τ ign and must also be considered. Experimental results from a study of the hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide (RGHP) are presented. Statistical analysis of the experimental data was conducted to evaluate the relative effects of RGHP concentration, initial ambient pressure, and the ambient gas on τ ign . At RGHP concentrations of less than 92% in water, stable ignition was difficult to achieve. At sufficiently high Lewis number, an oscillatory ignition process is observed. A phenomenological model comprising mixing, RGHP decomposition, fuel heating and vaporization, and auto-ignition is presented and compared to the experimental results.