Steps for FFT Analysis of Analog Input and Graph Display (4/5)

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Procedure

Step 7: Create Test Data
7-1. Create test data
7-2. Program assignment settings
7-3. Change the analog value capture part
Step 8: Graph the Test Data
8-1. FFT result at 1 kHz
8-2. 2 kHz graph
8-3. 50 Hz graph
Step 9: Data Actually Acquired from Analog Input
9-1. Input data from analog
9-2. FFT result

Step 7: Create Test Data

7-1. Create test data

Sysmac Studio FFT create test data — Add a high-speed analog unit (NX-HAD401) to the CPU rack

Add a new program and add the program below to create a test waveform
dummyPower is the waveform amplitude and dummyFreq is the frequency; change them freely to create test data
Values are put into the global arrays dummyAnalogInputValue_1_10 and dummyAnalogInputValue_10_20, which replace the high-speed analog unit inputs

// Create dummy analog data
// Program that creates a sine wave to check FFT operation

dummyPower := 10.0;			// Sine wave amplitude
dummyFreq := 1000.0;		// Frequency

FOR cnt := 0 TO 9 BY 1 DO
	dummyAnalogInputValue_1_10[cnt] := LREAL_TO_INT(SIN(DegToRad(dummyDeg)) * dummyPower);
	dummyDeg := dummyDeg + 0.036 * dummyFreq;
	IF dummyDeg >= 360.0 THEN dummyDeg := dummyDeg - 360.0; END_IF;
END_FOR;

FOR cnt := 0 TO 9 BY 1 DO
	dummyAnalogInputValue_11_20[cnt] := LREAL_TO_INT(SIN(DegToRad(dummyDeg)) * dummyPower);
	dummyDeg := dummyDeg + 0.036 * dummyFreq;
	IF dummyDeg >= 360.0 THEN dummyDeg := dummyDeg - 360.0; END_IF;
END_FOR;

7-2. Program assignment settings

Sysmac Studio FFT program assignment settings

Add the test program to the primary task

7-3. Change the analog value capture part

Sysmac Studio change analog value capture part

Comment out the high-speed analog unit inputs and change the analog input to the test data

FOR cnt := 0 TO 9 BY 1 DO
	//AnalogInputData[cnt] := INT_TO_REAL(N1_Ch1_Analog_Input_Value_1_10[cnt]);
	AnalogInputData[cnt] := INT_TO_REAL(dummyAnalogInputValue_1_10[cnt]);
END_FOR;

FOR cnt := 0 TO 9 BY 1 DO
	//AnalogInputData[10 + cnt] := INT_TO_REAL(N1_Ch1_Analog_Input_Value_11_20[cnt]);
	AnalogInputData[10 + cnt] := INT_TO_REAL(dummyAnalogInputValue_11_20[cnt]);
END_FOR;

Step 8: Graph the Test Data

8-1. FFT result at 1 kHz

This is the graph of the FFT result after turning FFTStart ON
The PowerSpectrum value is correctly large at 1 kHz

Sysmac Studio 1 kHz analog graph — 1 kHz analog graph

8-2. 2 kHz graph

Graph with the test data's dummyFreq changed to 2 kHz
Showing page 2

Sysmac Studio 2 kHz analog graph — 2 kHz analog graph

8-3. 50 Hz graph

Graph with dummyFreq changed to 50 Hz, below the high-pass filter cutoff frequency (100 Hz)
It is much smaller

Sysmac Studio 50 Hz analog graph — 50 Hz analog graph

Test data graph display complete

We were able to display the graph of the FFT results for the test data and the analog graph
Step 9 shows the results from actual analog input

Step 9: Data Actually Acquired from Analog Input

9-1. Input data from analog

Showing the first 500 ms of analog data
With actual analog input the input values are scaled; adjust according to the data you acquire

9-2. FFT result

Sysmac Studio horizontal axis of line graph

The acquired waveform seems to show components around 120 Hz, 240 Hz, 360 Hz... harmonics of 120 Hz
There is also a large component around 700 Hz
In this way we could see what components the waveform contains

On the next page

On the next page, we output the FFT results to a csv file and import it into Excel

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