User`s guide

Low Frequency Modulation Theory of Operation
This circuitry is used to record the time at which a measurement is made, in other words, each single
time measurement in a histogram is time stamped. A single histogram of a number of hits is gathered.
The statistical values from this histogram are recorded in the Summary view. The data in this tool is not
plotted as a histogram.
In Time View, the single measurements, or hits, are plotted in the order they occur. The software plots
the timestamp value on the x-axis and the measured period value on the y-axis.
In the FFT View, the frequency information is derived from the Time View.
Minimum Data Points determines the number of time measurements shown on Time View and refers
to the number of hits in the histogram.
Maximum Frequency determines the resolution of the plot in the FFT view or the time between
measurements in Time View.
Basically, changing the Maximum Frequency slows down the sampling rate—or increases the time
between measurements. The instrument then captures samples over a longer time and is able to
measure lower frequency information.
The first example shows 10 measurements spaced in time. This represents a single histogram of 10 hits
with the hits plotted on the x-axis in the order they were acquired starting from the left. It is apparent
that the period of the clock being measured is varying or modulated. This acquisition has not captured
an entire cycle of the modulation.
© WAVECREST Corporation 2005 Section 4 - GigaView
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