| 摘要 |
1450081 - Removing spurious pulses SIEMENS AG 20 Sept 1973 [20 Sept 1972] 44292/73 Headings G1N and G1U Spurious pulses are removed from a data signal, e.g. an ECG waveform, by an arrangement which, having detected the presence of a spurious pulse by the fact that its leading edge is sufficiently steep, effectively then zeroises the waveform for a pre-set period, e.g., 12msec., and then at the end of the pre-set period allows the waveform to return to its proper level smoothly, rather than abruptly, thereby both preventing the formation of secondary high frequency noise and reducing any long term transients resulting from the original spurious pulse. As shown in Fig. 2, an ECG waveform normally passes direct from a terminal 1, via an amplifier 19, to ultilisation devices 10, 11. The beginning of a spurious pulse with a sufficiently steep leading edge is detected by a differentiator 12, 13, rectifier 14 and threshold circuit 15, to set a 12msec monostable 16 on. This causes an FET 22 to conduct thereby applying 100% negative feedback to the amplifier 19 so that the data signal is zeroized. At the end of the 12msec period, FET 22 returns to its normal non-conductive state and the data signal is reapplied to the line 2. However, no abrupt change occurs because the amplitude of the data signal at the end of the 12msec period will be stored on a capacitor 24 and will be applied, via amplifier 19, in opposition to the data signal. Thus, the signal on line 2, which was zero during the 12msec reject period, gradually rises, as capacitor 24 discharges, to the valve of the data signal. |
