| 摘要 |
1376176 Analogue to digital converters SIEMENS AG 22 Nov 1971 [23 Nov 1970] 54207/71 Heading G4H Samples of the digital output of a counter Z are supplied at the frequency fg by switch Sch and store ZS to a D/A converter DAW, rather than allowing the converter to respond to every change of the counter output. When using a D/A converter of the type having a number of parallel connected weighted resistors switched in according to the counter output, where the electronic switches have a turn-on and turn-off delay thereby introducing errors, the invention reduces the overall error by reducing the amount of switching in the converter. The arrangement is used for the retro-active control of speed of an electric motor, where the difference between the desired speed represented by frequency f1 and the actual speed f2 derived by a tachogenerator is given by the output of the difference counter Z. |
