Analysis→Fft Graph Of Normal Electrode Configuration - Texas Instruments ADS131E08 User Manual

ADS131E08 Analysis Tools
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
where:
• f = input frequency
AIN
• f
SAMPLE
• N
WINDOW
• N
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.
26
Performance Demonstration Kit for the ADS131E08
Figure 27 shows the FFT display.
Figure 27 shows the Coherent Frequency Calculator. Coherent sampling in an
3:
TOTAL
= ADS131E08 sampling frequency
= number of odd integer cycles during a given sampling period
= number of data points (in power of 2) that is used to create the FFT.
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SBAU200B – June 2012 – Revised February 2016
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