Oscilloscope (dual channel, xy, time division,
trigger);
Spectrum Analyzer with amplitude and phase
display (linear, log, lines, bar, octaves band analysis 1/3, 1/6,
1/9, 1/12, 1/24);
Wave-form generator with "custom functions" plus
triangular, square, sinus, white noise and pulse generation (NO ALIASING:
the waveform are built using band-limited algorithms);
Frequency meter (in time and frequency domain) plus
counter;
Volt meter with rms and peak to peak readout;
Filtering (low pass, hi pass, band pass, band reject,
notch, "diode", DC removal;
Memo windows for analysis and file storage of
time series and spectrum;
A TRUE software digital analog conversion (for
complete signal reconstruction).
Frequency compensation; you can create/edit a custom
frequency response to apply to the spectrum analyzer.
VA main form (version 8.x.x)
(1) - Oscilloscope
Dual channel
Bandwith : depends from your soundcard (typical
20 Khz) up to 96 Khz (192 Khz sampling frequency)
Resolution from 8 bit (S/N 46 dB) up to 24
bit (S/N >120 dB)
Time division adjust according the sampling
frequency and sample resolution
Trigger (positive/negative slope) independent
for both channels
Complete software D/A of digital samples :
the Nyquist theorem allows reconstructing exactly the input signal
Utilities for quick frequency determination (hold
left mouse button down and move mouse to get frequency/amplitude)
Y-axis in Volt and percent full scale
Auto calibration of scope (and spectrum) in
volts (need an input signal of known amplitude)
(2) - Spectrum Analyser
Dual channel
Bandwidth : same as point (1) (oscilloscope
function): is the half
of the sampling frequency. Typical for 44100 Hz is 22050 Hz (up to 96 Khz)
Resolution from 8 bit (S/N 46 dB) up to 24
bit (S/N >120 dB)
X-axis in Hz, logarithmic and linear; zoom
x1..x16
Y-axis in dB or Volt (calibration needed);
linear/logarithmic; zoom
Average on spectrum up to 200 buffer
Direct window for amplitude with mouse
Autoscale
Capacity to modify the zero dB level
(manually/automatically)
Octave band analysis (1/1, 1/3, 1/6, 1/9, 1/12, 1/24)
(3) - Wave-form generator
Dual channel
Independent sampling frequency/resolution from
scope/spectrum (up to 192 Khz/24 bit)
Phase between channels (degree)
Direct real time generation/ loop with
predefined buffer
Waveform CUSTOM, built with harmonics (with
save/load in file ".fun" of defined waveform)
Modulation of custom waveform with
sinus/square/triangular
Real time parameters variation (amplitude,
frequency, phase between channels, type of waveform)
(4) - Frequency meter
Dual channel
Frequency meter in Hz/Time/Counter of the
input signal being visualized in spectrum/scope
Read the frequency of the harmonic of maximum
amplitude
Counter with threshold level
(5) - Volt meter (calibration needed)
Dual channel
Vpp, True Rms
Hold function
(6) - Filtering
FIR low pass cut-off frequency user defined
FIR high pass cut-off frequency user defined
FIR band pass cut-off frequencies user
defined
FIR band reject cut-off frequencies user
defined
IIR notch cut-off frequency user defined
IIR notch-inverted cut-off frequency user
defined
"Diode" function
DC removal
Dual filter (one for each channel)
(7) - Memo windows
Aquiring of spectrum with average
Edit offline (while VA running) of aquired
spectrum: zoom, navigate
Saving of spectrum in TXT format
Clipboard for aquired spectrum
Print of aquired spectrum
Mark points for each valid point (harmonic)
of spectrum
Aquiring of scope points (points aquired in
time domain)
Edit offline (while VA running) of aquired
time series: zoom, navigate
Saving of samples in TXT format
Clipboard for aquired samples
Print of aquired samples
D/A conversion: the points aquired may be
converted using Nyquist theorem for full reconstruction of signal in
time domain (see point 8 for D/A in real time)
(8) - real time DIGITAL/ANALOG conversion
D/A in real time
Dual channel
Allows visualizing each aquired harmonic
Points (8) need a clairification:
VA has the unbeatable feature to perform a full real time
Digital-Analog conversion for the oscilloscope function.
Consider using a frequency sampling of (standard)
44100 Hz, with a 16 bit resolution (resolution is not relevant for the purpose
of the discussion below...)
Other programs similar to VA simply plot the raw points on the screen, which
means you can’t easily analyze signals with a frequency higher than 3000/5000 Hz
(there are limited points to plot). Even worse, think a sinusoidal signal of 20
KHz. You would have only 2 points (more or less) per cycle! ... The Nyquist
theorem says that it is sufficient to RECONSTRUCT the original signal...try to see what
happens if you draw a sine with only two points ...it will appear like a
triangular waveform...
Try the power of VA enabling the function "full D/A", apply a sinusoidal signal
of 15-20 KHz (for example using the Waveform generator included in VA) finally
use the "Time division" control for the selected channel (mS/d) to display the
signal at the desired detail level. You will see a perfect waveform with all the
points of the original signal (not only two).
(9) Frequency compensation
Visual Analyser allows you to apply a predefined
frequency response to compensate (for instance) the frequency response of
a microphone. You should know the frequency response of your microphone;
normally professional microphone should be shipped with the typical frequency
response. You can add a limited number of points in VA, and apply. VA will
interpolate a continues curve by means of cubic spline interpolation
algorithm. You can do it through the windows below.
Latest VA reviews, articles:
Send an e-mail to
va@sillanumsoft.org
for questions and/or suggestions about the web site. The webmaster is Alfredo
Accattatis
Last modified: 02/03/09
Visual Analyser Project
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