| 摘要 |
A cathode ray oscilloscope deflection system selectively displays an integral number of cycles of a periodic or quasi-periodic input signal, regardless of the frequency of the signal. A wide band phase locked loop, synchronized to the input signal, generates pulses at a pulse repetition rate that is an integral multiple of the frequency of the input signal. A ripple counter converts the pulses into a staircase, x-axis deflection signal having a period equal to the duration of the number of cycles of the input signal selected for display and a predetermined maximum amplitude so that the x-axis of the scope is always swept the same distance regardless of the frequency of the input signal. The number of cycles displayed is determined by the repetition rate of the phase locked loop pulses relative to the frequency of the input signal. The repetition rate of the loop pulses is controlled by: (a) a first binary divider for controlling which of the fundamental or integral submultiple frequency of the input signal to which the phase locked loop is synchronized, and/or (b) a second binary divider circuit for controlling the pulse repetition rate of feedback pulses in the phase locked loop. Frequency or period of the input signal is displayed by a digital frequency or period meter that monitors the loop pulses.
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