Abstract: Establishing that pressure-influencing factors other than leakage of gas have stabilized before testing the integrity of a vessel in a system including the vessel, a reference vessel that can be connected to and isolated from the vessel, a common source of pressurized gas, a gauge to measure the difference between the vessel pressure and the reference vessel pressure and a computer capable of recording a series of pressure-difference measurements and mathematically manipulating them, the method including equalizing the pressures in the two vessels, then isolating them from each other for a preselected time period, then recording the pressure difference between them at the end of the time period, again equalizing the pressures and repeating that sequence until the pressure difference at the end of two consecutive time intervals is the same, thereby establishing that pressure-influencing factors other than leakage have stabilized.

Abstract: A sensor for chemical vapor detection using a surface acoustic wave (SAW) ray that provides a means for simultaneously detecting several chemical agents. The sensor has a piezoelectric substrate and a bidirectional surface acoustic wave transducer on the substrate. Also on the substrate are several pairs of identical acoustic sensing and reference channels each on opposite sides of the transducer in a mirror image fashion. Each channel pair has a thin film capable of absorbing a chemical vapor to be monitored and a metallic surface acoustic wave grating reflector capable of receiving and reflecting surface acoustic waves through the thin film and back to the transducer. An acoustic absorber separates each channel. The reference channels are protected from ambient conditions while the sensing channels are exposed to such conditions. An RF signal is applied to the transducer causing the propagation of an acoustic signal into each of the sensing channels and reference channels.