| 摘要 |
1365831 Producing visible displays from digital signals TEXACO DEVELOPMENT CORP 7 Jan 1972 [9 Feb 1971] 789/72 Heading G4H A visible display is formed from a set of digital words representing the equation; analogue value = ΠAG<SP>-E</SP> where G is constant and the digital word has some bits representing A, some bits representing E and a parity sign. A periodic reference signal V ref having a maximum and a minimum signal level is generated and is used to change a digital signal representing a number K every time V ref reaches its maximum. The signal representing A is entered into a shift register and is shifted by an amount K-E. The modified A is then converted to an analogue signal using V ref as reference voltage. The analogue values produced by a series of conversions are displayed on an oscillograph. The arrangement may be used for displaying seismic data. The digital word is stored in 18 stage register 20. Plus 8 volts is applied to comparator 34, and this is used to control sawtooth generator 32 producing a potential varying between 1 and 8 volts. The bits of signal A and parity sign S Πare entered into shift register 22. 3 Bit binary counter 26 is stepped by pulses from generator 32 and the output K of the counter is passed to subtractor unit 24 where E is subtracted from it. The resulting signal K-E is passed to shift register control 28 and shifts register 22 by the appropriate amount. After shifting the output of the register 22 is passed to D-A converter 30 and converted to analogue value V 0 . Signal V 0 is then passed to demultiplexer 38 and then to one of several chains of hold and filter circuits 42, 44 and thence to the oscillograph 46. The output of the converter may be averaged or the outputs of the filters summed and averaged and then used to control the frequency of generator 32. The signal K enables a fairly constant analogue output to be produced from the widely varying digital readings obtained from seismic readings as they decay. |
