| 摘要 |
A self-arming, prescaling frequency counter system comprises an armable frequency counter, an envelope detector, a prescaling pulse-shaper, and a delaying means. The envelope detector detects occurrence of an oscillating signal to be frequency measured and transmits an arming signal to arm the frequency counter for the duration of the oscillating signal. The prescaling pulse-shaper is coupled to receive the oscillating signal burst and generate a pulsed test signal of frequency an integer fraction of the oscillating signal frequency. The delaying means couples the test signal to the armable frequency counter input, delaying receipt of the pulsed signal burst until after the counter is armed, and delaying termination of the pulsed signal until after counter is disarmed. To minimize the width of the smallest signal burst which can be measured, the delay time is set approximately equal to the sum of the counter arming delay time, the counter disarming delay time and one cycle period of the lowest frequency signal to be measured by the counter. |
