Optics: measuring and testing – Inspection of flaws or impurities – Bore inspection
Patent
1974-04-16
1976-06-15
McGraw, Vincent P.
Optics: measuring and testing
Inspection of flaws or impurities
Bore inspection
250576, 1951035R, 356 36, 356 73, 356244, 356246, 195100, G01N 2106, G01N 100
Patent
active
039633551
ABSTRACT:
Microorganisms in a specimen are detected, identified, and enumerated by introducing the specimen into a sampling cartridge and diluting the specimen with a known volume of water within the cartridge. The cartridge has a manifold and several cassettes attached to the manifold. Each cassette contains a serpentine flow channel having a series of filters therein and a detection cell located downstream from each filter. The flow channel in each cassette also contains a culture medium which is freeze dried and is highly selective in the sense that it promotes the growth of one type of microorganism, but not others. The mixture of the specimen and water flows from the manifold into the flow channel of each cassette where it rehydrates the culture medium therein and further flows through the filters. Each filter removes a known proportion of the microorganisms from the mixture of specimen, water and medium, thereby effecting a serial dilution. After the cassettes are heated to incubate the microorganisms, the detection cells are observed for growth of the microorganisms therein which is manifested in a change in the light transmitting characteristics of the mixtures within the cells. This change is detected with great precision by projecting beams of light through the detection cells and measuring the current flowing through dedicated photocells located beyond the detection cells. The amount of current flowing through each photocell is proportional to the relative optical density of the mixture within the corresponding detection cell, and this density is plotted against time to give a unique time-related signature for each microorganism. Thus, the presence and identity of microorganisms in the detection cells is determined by mere changes in the optical density of the cells, whereas the number of microorganisms may be determined by considering the number of detection cells which change.
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Aldridge, Jr. Clifton
Gibson Sandra F.
Holen James T.
Jones Paul W.
Keyser George F.
McDonnell Douglas Corporation
McGraw Vincent P.
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