| 摘要 |
An electronic device for measuring rotational speed, in particular of internal-combustion engines for vehicles, has, for the purpose of stabilising the device for different motor types, in essence a resettable counter and a frequency divider which is fed from a quartz oscillator and outputs stepped-down counting pulses to a counting input of the counter. Control pulses, for example firing (trigger) pulses are applied to a reset input of the counter. Means for forming averages of the output pulses and displaying the average value are connected to one output of the counter. A second counter output is set up to block the counter. The counter generates output pulses having a width set in accordance with the step-down ratio of the frequency divider, specifically one such output pulse for each occurrence of a control pulse. A second counter, to which inverted control pulses are applied at its resetting input, can be used to double the frequency of the output pulses and to reduce the lower displayable rotational speed. <IMAGE>
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