FFT_Example_data_with_window - Example Problem - Generating...

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Unformatted text preview: Example Problem - Generating an FFT from a time signal - including windows J. M. Cimbala Answers: Useful number of data points for FFT: Given: 256 100 Hz Calculations for the frequency spectrum: 3 s 50 Hz The data points are provided below from an experiment. 0.39 Hz 128 Frequency spectrum: See Plot below. Summary about the input signal: 0.46 V 15.6 Hz 1.79 V 46.9 Hz 0.72 V Calculated values: DC = mean value of input signal = 0.4540 volts (average of all the useful input data) 300 256 2.56 s 0.01 Hz 0.39 Hz 50 128 Frequency Spectrum: (also divide first one by 2, and add back the DC value) frequency (Hz) 0.000-1.7527-2.2067-0.50315551210155 0.46 1 0.010-0.5650 0.39-1.0190 0.255239484675561-1.44005553334218E-002i 2 0.020 0.8801 0.78 0.4261-7.76383520072323E-003+1.97186040257435E-002i 3 0.030 3.1924 1.17 2.7384-4.77206890926481E-003-9.00947987812182E-003i 4 0.040 1.2804 1.56 0.8264 8.94397199299433E-003+4.6398488703775E-003i 5 0.050 0.9006 1.95 0.4466-7.625940404E-003+3.19708858117488E-003i 6 0.060-2.5214 2.34-2.9754 0.01-0.02 3.2332905736084E-002-1.50365761001296E-003i 7 0.070-0.4022 2.73-0.8562 0.01-0.01-3.7466315313763E-002-3.10360773236548E-002i 8 0.080-0.5707 3.13-1.0247 0.01-0.01 7.88264087543479E-003+3.46369883642316E-002i 9 0.090 3.2201 3.52 2.7661 0.01 0.03 3.35940007579051E-003-1.22673131637587E-002i 10 0.100 1.6182 3.91 1.1642 0.01 0.02 7.05476835049565E-003+1.75568281354845E-002i 11 0.110 1.6789 4.3 1.2249 0.02 0.02-2.70535057392308E-002-2.61735615253077E-002i 12 0.120-1.6800 4.69-2.1340 0.02-0.05 2.91556747126038E-002+1.28772322275302E-002i 13 0.130-1.2799 5.08-1.7339 0.03-0.04-1.45307213195953E-002-1.66941747572471E-003i 14 0.140-0.6754 5.47-1.1294 0.03-0.03 9.85750112550036E-004+1.72181037387782E-002i 15 0.150 1.6577 5.86 1.2037 0.03 0.04 1.74654914666632E-002-2.81921894958201E-002i 16 0.160 2.8238 6.25 2.3698 0.04 0.09-3.17427308096476E-002+8.93643772104044E-003i 17 0.170 1.3445 6.64 0.8905 0.04 0.04 1.07479807652269E-004+6.6854200995464E-003i 18 0.180 0.2188 7.03-0.2352 0.05-0.01 2.62823383690665E-002-8.55593579319265E-003i 19 0.190-2.4080 7.42-2.8620 0.05-0.15-3.05550464049493E-002+9.94209197515098E-003i 20 0.200-0.3065 7.81-0.7605 0.06-0.04 1.56197832849833E-002+1.94825876097873E-003i 21 0.210-0.1269 8.2-0.5809 0.06-0.04-1.61671990069486E-003-1.70549763019173E-002i 22 0.220 3.4371 8.59 2.9831 0.07 0.21-1.96182706309876E-002+2.54014121468286E-002i 23 0.230 1.3243 8.98 0.8703 0.08 0.07 4.24240023381379E-002-1.76080892116027E-002i 24 0.240 1.4993 9.38 1.0453 0.08 0.09-4.66701019348527E-002-1.08292385684645E-002i 25 0.250-2.2204 9.77-2.6744 0.09-0.24 2.64370828428918E-002+2.77830114842836E-002i 26 0.260-0.8385 10.16-1.2925 0.1-0.13-9.36904478246288E-003-8.61130181348074E-003i 27 0.270-0.7018 10.55-1.1558 0.11-0.12-2.40795877594664E-002-3.28476977244172E-003i 28 0.280 2.3923 10.94 1.9383 0.11 0.22 2.1994674106765E-002+6.76995487475133E-003i 29 0.290 2.3541 11.33 1.9001 0.12 0.23-2.91958319467153E-002-7.85366356044334E-003i 30 0.300 1.44721....
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This note was uploaded on 07/23/2008 for the course ME 345 taught by Professor Staff during the Spring '08 term at Pennsylvania State University, University Park.

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FFT_Example_data_with_window - Example Problem - Generating...

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