Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1974-10-15
1976-10-05
Krawczewicz, Stanley T.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 61R, 324 65R, G01R 2700
Patent
active
039847667
ABSTRACT:
Digital apparatus is disclosed which provides means for plotting the change with respect to time in the impedance ratio between a pair of cells, both cells of the cell pair containing a selected nutrient media and one (specimen) cell of the cell pair further including a micro-organism contaminant the growth of which is to be detected. Growth of the contaminant within the specimen cell over a selected period of time provides a characteristic change in the impedance of the specimen cell which provides, in turn, a corresponding change in the impedance ratio between the cells of the cell pair. Measurements are digitally made via means which compares the impedance ratio between the cells of the cell pair to successive resistive approximations of the ratio, and then outputs a digital word corresponding to the nearest approximation. Each digital word thus represents the impedance ratio at a given point in time of growth. At least a portion of the digital word or an arbitrary value indicative thereof is recorded with respect to time, for example, by electromagnetic means or as one point on a strip chart. Thus, a characteristic record is produced of the change with respect to time in the impedance ratio between the pair of cells caused by the particular micro-organism contaminant as it grows within the specific nutrient media of that pair of cells.
A plurality of cell pairs with both cells of each pair containing a nutrient media different from that in the other cell pairs and with the specimen cell of each pair containing the same micro-organism contaminant, may be sequentially and repeatedly sampled via the digital apparatus of the invention during a given period of time, wherein successive impedance ratios characteristic of contaminant growth in each media during such period of time are recorded. The combined record during such period of time defines a "signature" which is peculiar to the contaminant and comparisons of the "signature" with known "signatures" allows rapid identification of the contaminant.
REFERENCES:
patent: 2817810 (1957-12-01), Sontheimer
patent: 3443215 (1969-05-01), Bradley
patent: 3490039 (1970-01-01), Tsao
patent: 3652930 (1972-03-01), Sugiyama
patent: 3743581 (1973-07-01), Cady et al.
patent: 3784906 (1974-01-01), Ironside
patent: 3836847 (1974-09-01), Lucas
Bactomatic Inc.
Krawczewicz Stanley T.
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