| 摘要 |
1,170,111. Analogue-digital converters. COMPAGNIE GENERALE DE GEOPHYSIQUE. 4 Jan., 1967 [10 Jan., 1966], No. 599/67. Heading G4H. An anologue to digital converter system includes means for shifting the range of the reference signal so that it lies in the same range as the analogue voltage to be measured. In one embodiment (Fig. 1) both the unknown analogue voltage which may come from a geophone 1 and the reference signal from an oscillator 8 are fed via a variable gain amplifier 4, the gain of which is controlled by the analogue input voltage to an A/D converter 18. Members 9, 10, 11, 12 attenuate the signal from the oscillator 8 under the control of members 13, 14, 15, 16, the members 13 to 16 being controlled by the output from the converter 18 to bring the reference voltage into the required range. The converter 18 may be a well known A/D converter giving a parallel output on leads 25 to a recording system, e.g. a magnetic tape. In a further embodiment Fig. 2, in which the voltages from a plurality of geophones are converted to digital form by a single A/D converter under the control of multiplexing means, each input 31 is associated with a three-stage amplifier 38-40 and attenuator stages 45-48, the output of the amplifier, after filtering being applied to multiplexng means 61, 62 connected to a converter 66. The output of the converter is also connected to multiplexing means 70 which feeds the signal to the associated attenuator stages. |
