Download PicoScope User Guide

Dialog boxes
5.7
Spectrum analyser configuration
5.7.1
Spectrum Options
58
From the Settings menu, select Options....
This dialog box controls a number of optional features of the active spectrum analyser
window.
Note: These functions are not available on the spectrum analyser toolbar.
X scale
The X axis represents frequency. You can display the frequency either in linear or in
logarithmic form.
Y scale
On the spectrum analyser display, the Y axis represents the power at a specified
frequency. The power can be expressed either as volts (RMS), or as dB.
Window
PicoScope performs an analysis on a short block of samples. The 'cutting' of this block
from the data stream can introduce distortion which produces side-lobes on spectrum
peaks. This effect can be reduced by multiplying the block of data by a set of factors
which 'rounds off' the ends of the data. This technique is known as windowing.
PicoScope supports several different windowing methods. No windowing algorithm is
guaranteed to eliminate all end effects but switching between two methods can give a
clue to whether a particular peak is a side-lobe or a genuine peak. A rectangular window
is generally best for estimating an exact frequency, whereas a Blackman window is often
best for minimising side-lobes.
No of spectrum bands
A fast fourier transform divides up a signal into a number of frequency bands. More bands
gives higher resolution, but it is necessary to collect and process more data. This reduces
the display update rate, and reduces effectiveness when dealing with impulse-type
signals. You can select between 128 and 4096 frequency bands, in powers of two.
Copyright 2005 Pico Technology Limited. All rights reserved.
PSW044 v1.5