A method and apparatus for selectively detecting the presence and concentration of a constituent in a gas sample, such as for example the presence of the vapors emitted by explosives and drugs in the atmosphere. A sample flow is drawn through a switching device into a detector and the output of the detector is correlated with the operation of the switching device. The switching device is actuated at periodic intervals between first and second conditions. In the first condition the switching device interrupts the flow of the constituent of interest to the detector while allowing the remainder of the sample to pass into the detector. In the second condition all the gas sample passes into the detector. The changes in detector output result from the presence of the constituent and the magnitude of the changes indicate the concentration of the constituent in the gas sample.
6840456 - Injection valves - Owned by The United States of America as represented by the Secretary of the Army (Washington, DC)
An injection valve is provided. A first conduit is disposed between first and second chambers of the valve. An entrance to the first conduit is located within the first chamber. A second conduit is concentrically disposed within the first conduit so that there is a first flow passage between the first and second conduits connecting the first and second chambers. The second conduit has an entrance communicating with the first chamber via the entrance of the first conduit and an exit defining a first outlet port of the valve. A cover opens and closes a first inlet port of the first chamber, and a biasing device biases the cover closed. An actuator moves the cover from the closed position to open the first inlet port.
A hydrocarbon detector (20) includes a gas stream delivery element (26) configured to discharge a carrier gas (70) onto a surface (24). The carrier gas (70) serves to volatilize a hydrocarbon presence (22) from the surface (24). A gas stream recovery element (28) is configured to aspirate a sample gas (78) formed from the carrier gas (70) combined with the hydrocarbon presence (22) volatilized from the surface (24). A hydrocarbon sensor (58) detects the hydrocarbon presence (22) in the sample gas (78) and generates an output signal indicative of the hydrocarbon presence (22). An indicator (80) receives the output signal and indicates the hydrocarbon presence (22) in the sample gas (78). A heat source (72) coupled to the gas stream delivery element (26) heats the carrier gas (70) to further aid in the volatilization of the hydrocarbon presence (22).
A trace component dispensing system where a trace fluid in fluid is introduced into a carrier fluid by use of a controlling permeation member where the carrier fluid and trace fluid are continuously flowing and the trace fluid is transferred on at a selected permeation rate to the carrier fluid. In another aspect, tracer fluid dispenser capable of outputting a fixed rate of flow is utilized to input to a fluid in a fixed volume container for a predetermined period of time to establish a desired concentration of the trace fluid in the fixed volume container where the desired concentration is a function of the fixed rate of flow and the fixed volume container.
A process and device using back-diffusion for sampling a gas from an environment containing an aerosol of tramp material. The device cleans the tramp material from a barrier by the flow of a purge gas. The purge gas flow prevents diffusion of the tramp material through ports in the barrier through which the sample gas diffuses against purge gas flow. The purge gas continuously cleans the barrier, retards tramp material diffusion, and gathers and transports the sample gas.
As oxygen is an electron absorber it is desirable, when monitoring an atmospheric flow for the presence of tracer materials capable of detection in an electron capture detector, to remove the oxygen from the flow to the detector. The invention introduces a hydrogen supply directly into the atmospheric flow to allow the hydrogen to combine catalytically with the oxygen content of the flow to form water or water vapor. The thus formed water or water vapor is extracted from the flow proceeding to the detector. The reaction can occur within a palladium or palladium alloy conduit forming a part of the flow path to the detector.
