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Second Example PlugIn – Log-Log FFT Plot
A frequent requirement is to plot a frequency spe
ver
tical scale, so CustomDSO has only to change the horizontal one. Here is an example. The first figure has
be
en truncated on the right side.
These exam
ples were made with two different instrument setups: in the second, the FFT was zoomed vertically.
The graph has a red line to represent the theoretical envelope for the peaks. This has great potential for testing
the transmission characteristics of a
curve. Furthe
rmore, if the output is divided by the curve, the result for a perfect DUT would be a horizontal line,
which is ea
sy
to inspect. The example below has been magnified vertically by a factor of ten. The rise at the right
sid
e occurs because the signal is descending into the noise.
Private Sub Command1_Click()
'
Draw a DSO trace on a
Dim
WM As Object
Set WM = CreateObject("LeCroy.XStreamApplication")
Dim Samples As Long
Samples = WM.Math.F1.Out.Result.Samples
Samples = Samples - 1 ' Make it a round number.
'
Calculate the horizontal scale.
WRXi-OM-E Rev C
ctrum on two logarithmic scales. The instrument provides a
mplifiers and filters, since the output can be compared with a theoretical
logarithmic horizontal scale.
O
'
M
PERATOR
S
ANUAL
225
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