Thread: writing Marker values into a file with a N9000A CXA

you have the wrong forum - you should post your question to the Signal Analyzer Forum

Hi -

Are you referring to the Marker Logging feature?

Unfortunately CXA does not support this feature at present. CXA can log the measurement traces (up to 300) as spectrogram and store in a data file (one of the feature of option EDP), but it does not have marker information.

Regards -

Hi -

To get the Frequency/Amplitude data of a Marker/Trace can be done by using the instrument SCPI command. You can refer to the instrument Programmer’s Reference Manual for details of the format of the command. There is also a command to retrieve the system time of the instrument, however, it’s only in Sec, not ms. To get the more precise time of each event, user may need to use the specific function in their program to query the system time of the PC. The entire process would be:
1. Set the instrument to single sweep mode (INIT:CONT 0).
2. Initiate a new sweep (:INIT:IMM). And use *OPC? command to determine if the sweep is completed.
3. Query the marker/trace value by using the corresponding commands.
4. Use specific function (depends on the programming environment) to get the system time.
5. Log the marker/trace value along with the system time.
6. Turn to step 2.

By the way, Agilent’s N9342C/44C HSA (Handheld Spectrum Analyzer) offers the Marker Logging feature. Instrument can continuously record the frequency and amplitude value of the marker in the file. And if with GPS option, the data also contains the GPS location. Refer to the User’s Guide on page 110 for details:
http://www.home.agilent.com/agilent/redirector.jspx?action=ref&cname=AGILENT_EDITORIAL&ckey=1951260&lc=eng&cc=US&nfr=-11143.0.00&pselect=SR.GENERAL

Regards -

Thanks for the help, we have written the program and it works well. I include the core part (in C) below for anyone who might need something similar. Depending on the required BW/span/precision the speed is varying, for our application the fastest we can do is about 1 point/7 ms (without tracking the signal).

/*********************************************************************

• Program to perform a sweep and return the frequency and amplitude of the max, and track the signal
• 1. Perform a sweep
• 2. Write freq and amp of max into a file
• 3. Set centre frequency to freq of max
• Go to 1.
• 12/09/2012

**********************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include "visa.h"
#include <sys/timeb.h>

void main ()
{
/*program variables*/
ViSession defaultRM, viMXA;
ViStatus viStatus = 0;
double dMaxA = 0, dMaxf = 0, cfreq, BW, span, swetim;
int Nscan, i, swepoin;
struct timeb tmb;
int starts, startm, stops, stopm, tdiff, datatim;
char swetyp10;
FILE *out;

/*open session to GPIB device at address 18 */
viStatus=viOpenDefaultRM (&defaultRM);
/* viStatus=viOpen (defaultRM, "GPIB0::18::INSTR", VI_NULL,VI_NULL,&viMXA); */
viStatus=viOpen (defaultRM, "TCPIP0::169.254.65.165::inst0::INSTR", VI_NULL,VI_NULL,&viMXA);

/*check opening session sucess*/
if(viStatus)
{
printf("Could not open a session!\n");
exit(0);
}

/*increase timeout to 60 sec*/
viSetAttribute(viMXA,VI_ATTR_TMO_VALUE,60000);

/*Clear the analyzer*/
viClear(viMXA);

/*Clear all event registers*/
viPrintf(viMXA, "*CLS\n");

/*Stop continuous sweep*/
viPrintf(viMXA, "INIT:CONT OFF\n");

/*Ask for number of scans*/
printf("Number of scans?\t");
scanf("%d", &Nscan);

/*open output file*/
out = fopen("output.txt","a");

/*Get and print system parameters*/
viQueryf(viMXA, "FREQ:CENT?\n", "%lf", &cfreq);
viQueryf(viMXA, "FREQ:SPAN?\n", "%lf", &span);
viQueryf(viMXA, "BAND?\n", "%lf", &BW);
viQueryf(viMXA, "SWEep:TIME?\n", "%lf", &swetim);
viQueryf(viMXA, "SWE:POIN?\n", "%ld", &swepoin);
viQueryf(viMXA, "SWE:TYPE?\n", "%s", &swetyp);

ftime(&tmb);
datatim = tmb.time;

fprintf(out, "Date (s): %ld\nCenter frequency (Hz): %lf\nSpan (Hz): %lf\nBandwidth (Hz): %lf\nSweep Time (s) %lf\nSweep Points: %ld\nSweep Type: %s\n"
, datatim, cfreq, span, BW, swetim, swepoin, swetyp);

/*Display Off*/
viPrintf(viMXA, "DISP:ENAB OFF\n");

/*Get start time*/
ftime(&tmb);
starts = tmb.time;
startm = tmb.millitm;

/*Loop of scans*/
for(i=1; i <= Nscan; i=i+1)
{
/* Initiate a sweep and wait for it to complete*/
viPrintf(viMXA, "INIT:IMM;*WAI\n");

/* Do a peak search */
viPrintf(viMXA, "CALC:MARK1:MAX\n");

/* Save frequency and amplitude of Mark1 into variables */
viQueryf(viMXA, "CALC:MARK1:Y?\n", "%lf", &dMaxA);
viQueryf(viMXA, "CALC:MARK1:X?\n", "%lf", &dMaxf);

/* Write the freq and amplitude at Marker 1*/
fprintf(out, "%lf\t %lf\n", dMaxf, dMaxA);
//printf("%lf\t %lf\n", dMaxf, dMaxA);

/* Center the display, only required if you need to track the signal*/
viPrintf(viMXA, "FREQ:CENT %lf Hz\n", dMaxf);
}

/*Get stop time, calculate time it took*/
ftime(&tmb);
stops = tmb.time;
stopm = tmb.millitm;
tdiff = (stops-starts)*1000 + (stopm - startm);
printf("timediff = %ld (milliseconds)\n", tdiff);

/*close output file*/
fclose(out);

/*Display On*/
viPrintf(viMXA, "DISP:ENAB ON\n");
viPrintf(viMXA, "INIT:CONT ON\n");

/* Close session */
viClose (viMXA);
viClose (defaultRM);
}