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The effect of space radiation on the reliability of microelectromechanical systems (MEMS) devices is an important consideration for future upper atmosphere and space applications. MEMS capacitors with insulator materials of silicon nitride (\ Si3{\ {N}}4), silicon oxide (\ SiO2), and ultrananocrystalline diamond (UNCD) were selected for radiation and leakage current studies. Leakage current was used as a measure of insulator performance and reliability, and is suggested here as a method to detect charge trapping, which also affects reliability. UNCD capacitors were orders of magnitude leakier than \ Si3{\ {N}}4 and \ SiO2, with \ Si3{\ {N}}4 being leakier than \ SiO2. \ SiO2 devices exhibited unstable leakage current with accumulated electric field stress, and were not utilized in radiation studies. \ Si3{\ {N}}4 capacitors exhibited leakage current decay (with a time constant of 190 s) under constant voltage stress above 2 MV/cm due to charge injection from the electrodes and trapping in the insulator. \ Si3{\ {N}}4 and UNCD capacitors were more sensitive to ionizing gamma radiation than to displacement damage from fast neutrons. Both \ Si3{\ {N}}4 and UNCD devices survived total doses of radiation representative of 20–100 years in the Van Allen radiation belts with 4 mm Al equivalent shielding. Capacitor equivalent circuit and resistor capacitor (RC) circuit charging models are developed to explain leakage current behavior of \ Si3{\ {N}}4 capacitors subjected to constant voltage stress and/or irradiation. In situ monitoring of \ Si3{\ {N}}4 capacitors placed next to the nuclear reactor core did not yield any single event effects at electric field strength of 1 MV/cm with a fast neutron fluence of 2\times 10^12\ \ n/cm^2. \ Si3{\ {N}}4 MEMS capacitors appear best suited for upper atmosphere and space applications with their relatively low leakage current (low power consumption) and apparent radiation hardness. [ABSTRACT FROM PUBLISHER]

The response time of a pressure sensor is required when it is used in control systems and in some measurement applications. It is often difficult to measure the response time of a pressure sensor since it is difficult to obtain changes in fluid pressure sufficient to characterize the sensor dynamic response. In this article we describe a relatively simple system for measuring or validating the response time of pressure sensors with fast dynamic response. The system consists of two chambers isolated by a graphite rupture disk, a device that fully and rapidly opens at a known rupture or break pressure. A pressure transient in the second chamber is initiated by slowly increasing the pressure in the first chamber until reaching the nominal break pressure of the rupture disk. Performance of the system was validated by comparing the rise time predicted by a theoretical model with the rise time of the pressure transient measured by a piezoelectric pressure transducer. The method was evaluated by comparing the response to the pressure transient of an optical based pressure transducer with the response of the reference piezoelectric pressure transducer. The time constant of the tested fiber optic pressure sensor was found using the method presented in this article to be 0.488 ms, which is close to the time constant of 0.455 ms measured by a comparison method. [ABSTRACT FROM AUTHOR]