Calculation; Improving The Accuracy Of Time Interval Measurements - HP 64700 Series User Manual

Calculation

I mproving the
1
Accuracy of Time
Interval
Measurements
To measure longer intervals, the sample period must be increased.
Resolution is formally defined as:
resolution = + /- (sample period + skew).
A high sample rate (100 MHz), coupled with low skew (plus or
minus 4 ns for both opposite and same direction transitions), gives
the timing analyzer very good resolution.
You can improve the accuracy of an interval measurement by
making the measurement with a series of repetitive executions.
When a single execution is made, the resolution is equal to
+ /-(sample period + skew). When measuring a stable interval
using a series of repetitive executions, the accuracy of the
measurement improves by the following:
accuracy = + /-(((sample period)/sqrt(n)) + skew)
where:
sample period is the sample period specified in the timing
analyzer trace specifications.
sqrt(n) is the square root of the number of
executions included in the measurement.
skew is the delay differences between input
channels.
A tenfold improvement (x10) is obtained in the accuracy of your
measurement when using one hundred repetitive executions for the
measurement.
Accurate Timing Measurements D-3