Phase Measurements - Racal Instruments 2251A Operator's Manual

PHASE MEASUREMENTS

A phase measurement consists of:
Ratio Measurement: To ensure that the two input signals are of the same frequency
(within 10%)
Period Measurement: to determine the period of signals
Time Interval Measurement: To determine the time difference between two signals.
Thus, the phase measurement time consists of the summation of the above three
measurement times.
For the ratio and period measurement, gate time is automatically set a 1 mS.
NOTE: A general idea of the phase characteristic or the time difference between the
two signals is required in order to calculate the measurement time.
EXAMPLE:
Signal Frequency of Both channels: 1 MHz
Auto-trigger Channel A: 500 mS
Auto-trigger Channel B: 500 mS
Processing Time: 50 mS
Expected Phase Difference: 90E
Phase = [(Time Interval)(360E)/(Period)]
Time Interval = [(Phase)(Period)/(360E)]
Time Interval = [(90E)(1FS)/(360E)]
Time Interval - 250 nS
Time Interval Meas. Time: 250 nS
Ratio Meas. Time = Gate Time + 2 Periods of Slower Signal
Ratio Meas. Time = 1 mS + 2 (1 FS)
Ratio Meas. Time: 1.002 mS
Period Meas. Time = Gate Time + 2 Periods of Signal
Period Meas. Time = 1 mS + 2 (1 FS)
Period Meas. Time: 1.002 mS
Phase Meas. Time = 1.002 mS + 1.002 mS = 250 nS
Phase Meas. Time = 2.004250 mS
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= = > Period: 1 FS