How to Measure Power using FETCh and READ VISA Programming Examples
Agilent 8163A/B, 8164A/B & 8166A/B Mainframes, Fifth Edition 195
How to Measure Power using 
FETCh and READ
The example shows the difference between a "FETCh" and a "READ" 
command. 
Install a power meter in Slot 1, before executing this example. 
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <visa.h>
/* function prototypes for this examples */
/* function for a simple error handling explained in example 1 */
void checkError(ViSession session, ViStatus err_status );
void main (void)
  {
  ViStatus       errStatus;     /* returned error code from visa call */
  ViSession      defaultRM;     /* default visa resource manager 
variable */
  ViSession      vi;            /* current session handle */
  ViChar         replyBuf[256]; /* buffer holding answers of the 
instrument*/
  ViChar         compBuf[256];  /* buffer used for comparsion */
  ViChar         c;             /* used in the keyboard wait loop */
  ViReal64       averagingTime; /* averaging time */
  ViInt32        i;             /* loop counter */
    errStatus = viOpenDefaultRM (&defaultRM);
    if(errStatus < VI_SUCCESS)
      {
        printf("Failed to open VISA Resource manager\n");
        exit(errStatus);
      }
    errStatus = viOpen (defaultRM, "GPIB::20::INSTR", 
VI_NULL,VI_NULL,&vi);
    if(errStatus < VI_SUCCESS)
      {
        printf("Failed to open instrument\n");
        exit(errStatus);