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5.3
FFT Tool
The FFT subtab displays the data in the frequency domain by performing an FFT on the eight channels.
Details of the FFT, including SNR, THD, and more, can be viewed using the FFT Analysis button located
at the bottom of the display.
Figure 27. Analysis→FFT Graph of Normal Electrode Configuration
5.3.1
Coherent Frequency Calculator
The red box labeled 1 in
FFT is defined in
Equation
f
N
AIN
WINDOW
=
f
N
SAMPLE
TOTAL
where:
•
f
= input frequency
AIN
•
f
= ADS130E08 sampling frequency
SAMPLE
•
N
WINDOW
•
N
= number of data points (in power of 2) that is used to create the FFT.
TOTAL
If the conditions for coherent sampling can be met, the FFT results for a periodic signal are optimized. The
ideal A
frequency is a value that is calculated based on the sampling rate so that the coherent sampling
IN
criteria can be met.
SBAU202 – June 2012
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Figure 27
shows the FFT display.
Figure 27
shows the Coherent Frequency Calculator. Coherent sampling in an
3:
= number of odd integer cycles during a given sampling period
Copyright © 2012, Texas Instruments Incorporated
ADS130E08 ANALYSIS TOOLS
Performance Demonstration Kit for the ADS130E08
(3)
27
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