Example: Frequency Response
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10 ! *********************************************************************
20 ! Example: Frequency Response
30 !
40 ! This program generates a theoretical frequency response
50 ! display (response in dB vs. frequency in Hz) for two channels.
60 !
70 ! ************************************************************
80 !
90 REAL Freq(1:31),Channel_1(1:31),Channel_2(1:31)
100 !
110 ! Define test frequencies.
120 !
130 DATA 20,25,32,40,50,63,80,100,125,160
140 DATA 200,250,320,400,500,630,800,1000,1250,1600
150 DATA 2000,2500,3200,4000,5000,6300,8000,e,12500,16000,20000
160 READ Freq(*)
170 !
180 ! Take voltage measurements for both channels, convert to dB.
190 !
200 FOR I=1 TO 31
210 Channel_1(I)=20*LGT(FNMeasure(Freq(I),1))
220 Channel_2(I)=20*LGT(FNMeasure(Freq(I),2))
230 NEXT I
240 !
250 ! Create and set up the graph
260 !
270 ASSIGN @Graph TO WIDGET "XY GRAPH";SET ("SHARED X":1,"VISIBLE":0,"TITLE":" Example: Frequency Response","WIDTH":400,"HEIGHT":300)
280 CONTROL @Graph;SET ("SYSTEM MENU":"Quit")
290 ON EVENT @Graph,"SYSTEM MENU" GOTO Finis
300 !
310 ! Set X axis attributes
320 !
330 CONTROL @Graph;SET ("CURRENT AXIS":"X","AUTOSCALE":1,"LOGARITHMIC":1,"AXIS LABEL":"Frequency (Hz)")
340 !
350 ! Set Y axis attributes
360 !
370 CONTROL @Graph;SET ("CURRENT AXIS":"Y","AUTOSCALE":1,"AXIS LABEL":"Response (dB)")
380 !
390 ! Enter the data into the graph
400 !
410 CONTROL @Graph;SET ("X DATA":Freq(*))
420 CONTROL @Graph;SET ("CURRENT TRACE":1,"Y DATA":Channel_1(*),"TRACE LABEL":"Channel 1")
430 CONTROL @Graph;SET ("CURRENT TRACE":2,"Y DATA":Channel_2(*),"TRACE LABEL":"Channel 2")
440 !
450 ! Display the graph
460 !
470 CONTROL @Graph;SET ("VISIBLE":1)
480 LOOP
490 WAIT FOR EVENT
500 END LOOP
510 Finis: END
520 !
530 ! This function simulates some data for the use of this program
540 !
550 DEF FNMeasure(Freq,Chan)
560 !
570 ! Simulate measured data for second order lowpass filters
580 !
590 F=Freq*(.8+Chan/5)
600 RETURN 1/(1-F/(3000-Chan*400)+(F/3000)^2)
610 FNEND
