Velleman PCSU1000 DSO User Manual

Page 12

PC Oscilloscope PCSU1000

if the amplitudes are very different, a window with low sidelobes will reduce leakage around the large
component, and should make the small one easier to detect.

Comparison of the window functions

Window type

Window characteristics

Applications

Rectangular

Narrow mainlobe
Slow rolloff rate

Broadband random (white noise)
Closely spaced sine-wave signals

Bartlett

Narrow mainlobe
Fast rolloff rate

Hamming

Good spectral resolution
Narrow mainlobe

Closely spaced sine-wave signals

Hanning

High maximum sidelobe level
Good frequency resolution
Reduced leakage
Fast rolloff rate

Narrowband random signals
Sine wave or combination
of sine-wave signals

Blackman

Wide mainlobe
Fast rolloff rate

Flat top

Good amplitude accuracy
Wide mainlobe
Poor frequency resolution
More spectral leakage

Sine wave with need
for amplitude accuracy

FFT Options

Maximum

Maximum value of each frequency is displayed in Run mode.
This option can be used for recording signal levels as a function of frequency (Bode plot). You can
use spreadsheet to display the frequency response curve including the frequency labels. On File
menu, click Save FFT Data to export the data to the spreadsheet.

RMS Average

Use this averaging mode to reduce signal fluctuations.
RMS averaging provides an excellent estimate of the true signal and noise levels of the input signal.

Vector Average

Use this averaging mode to reduce random or uncorrelated noise in the synchronous signal you want
to display.
Vector averaging requires a trigger - set Trigger ON.
The signal of interest must be both periodic and phase synchronous with the trigger.
Vector averaging reduces the noise floor for random signals since they are not phase coherent from
time record to time record.
If not trigged, the signal will not add in phase and instead will cancel randomly.

Hardware setup

Select the LPT port where the hardware is connected.

Operation mode

Oscilloscope connected to USB port.

Demo mode. (No hardware needed).