HP 54750A, User Manual, Page: 239 / 478

Increasing Measurement Accurac y
and Time-Interval Measurement
Increasing Measurement Accuracy
T o see the variable jitter , set P osition in the Time Base menu to a large
number relative to the Scale setting. As you increase the value of P osition,
you will see the jitter increase . The instrument's variable jitter is on the
order of 10 to 20 ppm, so you must use a large value of P osition and a fast
setting of Time Base Scale to see it. Y ou can use the automatic measurements
in the instrument to measure the jitter and observe its statistics . T o calculate
the slope of the variable jitter , subtract the xed jitter from the observed
jitter and divide by the P osition setting.
The jitter in the instrument has approximately normal distribution. F or
measuring jitter that also has a normal distribution, the standard deviations
add in quadrature as shown in equation 1.
Equation 1 (M easur ed j itter )
2
= (S ig nal j itter )
2
+ (S cope j itter )
2
If the standard deviation of the instrument's jitter is 1/3 of the standard
deviation of the actual jitter , the error in the measured standard deviation
will be about 5 percent.
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