AnsweredAssumed Answered

Spectrogram Display Function

Question asked by sushio on Jun 16, 2007
Latest reply on Jun 25, 2007 by MikeHall
Hi all,

I don't know if anyone has noticed this before or not.
In the Spectrogram display mode for spectrum, the
x-axis is the frequency domain, and the 'y'-axis is the
time domain. (the 'y' here is different from what it defines
in the marker object) As time goes by, the spectrogram keeps
updating the colored row at the bottom as the latest spectrum.
So far so good.

Now is the confusing part. I was trying to find out what's affecting
the delta_t on the 'y'-axis(which is the time interval between two
consecutive colored rows). Two parameters I noticed: "Fixed Height"
and "Buffer Depth". After playing around with these two and examine
the reading with markers, I found out that although the time domain
blocks seem to be evenly chunked into different rows/traces graphically
, the timestamp associated with each of them are not evenly spaced!

In other words, the delta_t is not a constant, although the total time
difference of the range of displayed is correct ( the fixed height reading ).
Is this the natural behavior of the VSA software or did I miss any key
issues here?

Not only that, originally I though each trace(row) of spectrogram
should be equal to a complete sweep in time domain (in the case of
displaying spectrum as spectrogram). However, if I take
the Main Time Length(time to complete one sweep) * the Buffer Depth
(number of traces displayed/buffered)
the result is not equal to the Fixed Height.
So confused now...don't know if the time stamp information
is valid or not at all.

Any suggestions or opinions? Please advise. Thank you so much!