9.1 Time,Frequency,and Phase-Angle Measurement 5/35 Crystal oscillator 10 MHz Gote Decimal-counting units 回回回回回回回 Signal Gote Amplifier open closed Signal Gate and Trigger control shaper level Time Irigger-level control -0.0860314sec+ Fig.9.1(b)Period Measurement The trigger-level control is adjusted so that triggering occurs on the steepest part of the signal waveform to reduce error. Define frequency fo=/fc,fc is the frequency of crystal oscillator,for a 1-s sampling period,when f>fo frequency should be measured and when f<fo,period should be measurement to get better accuracy. 6/35 9.1 Time,Frequency,and Phase-Angle Measurement Crystal oscillator 10 MHz Gate 回回回回回回回 Slope Gate control Input 4 signal 1 Trigger Stop Amplifier and shaper Trigger-level control 路di计 Trigger Slope+、 Amplifier and shoper Trigger-level control 0.0074319sec (c)Time-interval measurement Fig.9.1(c)Time-Interval Measurement Two separate events have been transduced to electrical pulses.One is used to open the gate and the other is used to close the gateFig. 9.1(b) Period Measurement - The trigger-level control is adjusted so that triggering occurs on the steepest part of the signal waveform to reduce error. - Define frequency ࢌ = ૙࡯ࢌ , fC is the frequency of crystal oscillator, for a 1-s sampling period, when f>f0 frequency should be measured and when f<f0, period should be measurement to get better accuracy. 9.1 Time, Frequency, and Phase-Angle Measurement 5/35 9.1 Time, Frequency, and Phase-Angle Measurement Fig. 9.1(c) Time-Interval Measurement Two separate events have been transduced to electrical pulses. One is used to open the gate and the other is used to close the gate 6/35