Agilent Technologies ESA-E Series Programmer's Manual page 145

Programming Example s
Measuring Harmonic Distortion (RS-232)
TakeSweep() ;
/* Signal track off * /
viPrintf(viESA,"CALC :MARK :TRCK :STAT OFF\n") ;
/*Reset timeout to 3 sec* /
viSetAttribute(viESA,VI ATTR TMO VALUE,3000) ;
/*Perform a peak search and wait for completion* /
viPrintf(viESA,"CALC :MARK :MAX\n") ;
/*Set marker amplitude in Volts* /
viPrintf(viESA,"UNIT :POW V\n") ;
/*Query and read the marker amplitude in Volts* /
/*Store the result in the fHarmV array .*/
viQueryf(viESA,"CALC :MARK :Y?\n","%lf", &fHarmV[lNum]) ;
/*Change the amplitude units to dBm * /
viPrintf(viESA,"UNIT :POW DBM\n") ;
/* Read the marker amplitude * /
viQueryf(viESA,"CALC :MARK :Y?\n","%lf", &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[1Num] = 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*/