Uni-T UTD2052CEX [36/120] Operating manual for utd2000 3000

Operating Manual for UTD2000/3000

Selection of FFT window

Mathematical storage oscillograph will carry out FFT conversion for time record with limited length when

assuming continuous repetition of YT waveform. YT waveform will have the same amplitude in beginning

and ending locations for no interrupation. However, high-frequency transient interruption will be caused in

connector due to different waveform amplitudes for non-integral cycle of YT waveform. Such effect shall be

called as leakage in frequency domain. T herefore, value in forced b eginning and ending locations is 0 b

multiplying original waveform by a window function to avoid leakage. Please r efer to following form for

application of window function

Form 2-

FFT window

Characteristic

The most appropriate measurement content

Rectangle

The best frequency and the poorest

amplitude resolution to be basicall

similar to circumstances without window

;

Transient or short impulse with basically equivalent

signal level; Sine with equivalent amplitude wit

similar frequency; Wide band random noise of wave

spectrum with slow variation

;

Hannin

With excellent frequency resolution and

poor amplitude resolution by comparin

with r ectangular window

;

Sine, cycle and narrow band random noise

Hammin

Frequency resolution of Hamming window

is better than that of Hanning window slightly

Transient or short impulse with large difference

for signal level

;

Blackma

The best amplitude resolution and the

poorest frequency resolutio

Mainly used for single-frequency signal to search

for higher order of harmonic wave