GB1470071A - Monitoring counters - Google Patents

Abstract

1470071 Counting apparatus AUSTRALIA COMMONWEALTH OF 9 April 1974 [10 April 1973] 15729/74 Heading G4D [Also in Division H3] In monitoring a fluctuating electrical signal, such as from a strain gauge sensing stresses in an aircraft structure, so called range pairs are detected and individually counted. A range pair is an excursion of the signal beyond a first level followed by an excursion in the opposite direction beyond a second level (Fig. 2); within certain limitations one crossing of each level is sufficient to identify. In practice the signal is applied to a plurality of different level detectors, range pairs can then be found for any pair of levels although small fluctuations may be ignored by not counting any with levels close together. In order to identify pairs the outputs of the n level detectors may be applied to both the row and column of an n Î n triangular matrix of bi-stable circuits; the crossing of a level by the signal then sets all the bi-stables in the row and resets all those in the column. The resetting of a bi-stable which was set at a previous crossing is detected and applied to a counter associated with that particular bi-stable. A large number of counters is required to count all possible range pairs from a large number of strain gauges necessary to monitor a complete aircraft. Therefore in a detailed embodiment (Figs. 7-14, not shown), the individual counts are stored in a memory such as a core store, protected against cessation of power supply and a count to be incremented is read into a register, incremented and returned to the memory. A time division multiplex arrangement allows several strain gauge channels to operate simultaneously. The total counts may when required be printed or recorded on a tape cassette for later analysis by a computer to determine the condition of the aircraft.