BOOSTXL-ADS7841-Q1 EVM GUI Operation
18
SNAU229 – December 2017
Copyright © 2017, Texas Instruments Incorporated
BOOSTXL-ADS7841-Q1 BoosterPack™ User's Guide
4.4.1
FFT Analysis Settings and Controls
Sample Rate -
This field indicates the sampling frequency of the ADC data (kHz)
Samples -
The FFT requires a time domain record with a number of samples that is a power of 2. The
Samples drop-down menu provides a list of values that satisfy this requirement.
Fund Freq (kHz) -
This field displays the frequency of the largest amplitude input signal computed from
the FFT data, typically the fundamental frequency.
Window -
The window function is a mathematical function that reduces the signal to zero at the end
points of the data block.
In applications where coherent sampling cannot be achieved, a window-weighing function can be applied
to the data to minimize spectral leakage. The following options are available:
•
Rectangular
•
Hamming
•
Hann
•
Blackman
•
7-Term Blackman-Harris
For a more thorough discussion of windowing, refer to IEEE1241-2000
Harmonics
This field sets the number of harmonics that are included in the FFT performance calculations.
4.5
Histogram Analysis
The
Histogram Analysis
page creates a histogram of the captured channel data and displays it. A
histogram is merely a count of the number of times a code has occurred in a particular data set. The
following parameters of the captured data set are displayed:
•
The
Std Dev [
σ
]
displays the standard deviation of the data set. This value is equivalent to the RMS
noise of the signal when analyzing a dc data set.
•
The
Mean
displays the average value of the data set.
•
The
Median
displays the median value of the data set.
•
The
Code Spread
displays the peak-to-peak spread of the codes in the data set; for a dc data set, this
range would be the peak-to-peak noise.
