Agilent Technologies Model A.08.xx manual 176

Programming Examples

Measuring Harmonic Distortion (RS-232)

/*Query and read the marker amplitude in Volts*/ /*Store the result in the fHarmV array.*/ viQueryf(viESA,"CALC:MARK:Y?\n","%1f", &fHarmV[lNum]);

/*Change the amplitude units to dBm */ viPrintf(viESA,"UNIT:POW DBM\n");

/* Read the marker amplitude */ viQueryf(viESA,"CALC:MARK:Y?\n","%1f", &fHarmDbm[lNum]);

}

/*Sum the square of each element in the fHarmV array and calculate the relative amplitude of each harmonic relative to the fundamental*/

for (lNum=2;lNum<=lMaxHarmonic;lNum++)

{

dSumSquare= dSumSquare + (pow (double(fHarmV[lNum]) ,2.0));

/* Relative Amplitude */

fRelAmptd[lNum] = fHarmDbm[lNum] - fFundaAmptdDbm ;

}

/*Calculate the total harmonic distortion by dividing the square root of the sum of the squares (dSumSquare) by the fundamental amplitude in Volts (dFundaAmptdV).Multiply this value by 100 to obtain a result in percent*/ dPrcntDistort = ((sqrt(double (dSumSquare))) /dFundaAmptdV) *100 ;

/*Fundamental amplitude in dBm */

printf("\nFundamental Amplitude: %lf dB \n",fFundaAmptdDbm);

/*Fundamental frequency in MHz*/

printf("Fundamental Frequency is: %lf MHz \n",dFundamental/10e5);

/*Relative amplitude of each harmonic in dBc*/ for (lNum=2;lNum<=lMaxHarmonic;lNum++)

printf("Relative amplitude of Harmonic[%d]: %lf dBc \n",lNum,fRelAmptd[lNum]);

/*Total harmonic distortion in percent*/

printf("Total Harmonic Distortion: %lf percent\n",dPrcntDistort);

/*Close the session*/ viClose(viESA); viClose(defaultRM);

}

176 Chapter 3