Metrix OX9302-BUS, User Manual

Page: 22 / 143

Functional Description
22
Use this mode to display extreme values of the signal, acquired between two samples of the
acquisition memory.
This mode is used:

to detect a false representation due to undersampling

to display events having a short duration (Glitch,
≤
2ns).
Whatever time base is used, with its corresponding sampling rate, events having a short
duration (Glitch,
≤
2ns) are displayed.
ROLL : Automatic on time base > 100ms, single
In single-shot mode, if the time base exceeds 100ms/div, the new samples are displayed as
soon as they are acquired and the ROLL mode is activated when the acquisition memory is
full (scrolling of the trace from right to left on the screen).
In triggered mode, save/retrieve can be used to record acquisitions in .trc format. to the
"Traces" directory
This lets you store several rare events in the file system and analyse them later.
2. Y(f) = FFT (Fast
Fourier Transform)
The
Fast Fourier Transform (FFT) is used to calculate the discrete representation of a
signal in the frequency domain from its discrete representation in the time domain. It is
calculated on 2500 points.
It can be used in the following applications:

measurement of the various harmonics and of the distortion of a signal,

analysis of a pulse response,

the search for a noise source in logical circuits.
The Fast Fourier
Transform
is calculated
using the formula
X (k) =
1 2
2
2
1
N
x n j
nk
N
n
N
N
* ( ) * exp
−




=−
−
∑
π
for k
∈
[0 ( N –1)]
x (n): a sample in the time domain
X (k): a sample in the frequency domain
N: resolution of the FFT
n: time-domain index
k: frequency index