AEQ Audio Over IP
Routing System
55
About the Histogram.
The horizontal axis of the histogram shows
the distribution of clock frequency offset
measurements against the nominal frequency
of the clock, in parts per million (ppm). The
zero point of the horizontal axis corresponds
to the clock's nominal frequency (i.e. the
frequency that the clock is intended to run at,
for example, 48 kHz).
The vertical axis shows the number of
measurements recorded at each data point,
on a logarithmic scale.
The histogram is continually updated, with
measurements taken roughly once per
second.
• To select devices, click the drop-down
menu at the top.
• To clear the histogram, click Clear.
• To save a png format screenshot of the
current data, click Save.
Interpreting the histogram.
The histogram can be seen as an indication of how
much work a slave clock is doing to stay in sync with
the master clock.
Generally, a stable and accurate clock will show
consistently very low offset (in the order of a few
ppm). It means that the clock's nominal frequency
closely matches the master clock, and it is not
having to change its offset very much to stay in sync.
A histogram that shows a distributed range of offsets
indicates an unstable clock - it is having to change
its
offset significantly, and often, to stay in sync with the
master clock. This can be due to overloaded network
links, or poorly-implemented EEE.
A histogram that shows measurements in amber
and/or red indicates a clock that might be currently
stable, but has little room for manoeuvre; its offset
could easily move outside its pull range, at which
point it will lose sync completely. This can result
when the master clock is derived from an inaccurate
external word clock.
To Next Page
Loading...
Need help?
General
