Generating autonomous sweep function with 8648A using GPIB

[ms1]

Hi,

I'm using a signal generator (HP 8648A)  with GPIB compatibility. I currently have LabVIEW ver 6.1 and have been able to establish rudimentary control with LabVIEW's GPIB read and write functions. What I would like to do is to generate an AM signal that changes the RF incrementally from 80MHz to 1GHz in steps of my choosing 1k / 1M etc. I have looked extensively through the manual and seem to be able to use any write command or read query that is mentioned. However, these can only be written individually into LabVIEW's front panel command box for the GPIB write data stream. I have been trying to set up a loop structure that increments the frequency in accordance with the desired step freq but to no avail. Is there a way to do this as I am only new to LabVIEW. It seems that the variable that needs to change on each loop iteration can not be touched because it is within a text string. Is there a way around this? for example: I can issue several commands such as freq:cw 80 MHZ; freq:cw 81MHZ; that both as you can imagine change the RF frequency to 80Mhz then 81MHz. So in theory it is possible to set all of my frequencies up to 1GHz but this requires me typing a similar instruction 920 times. This defeats the purpose of autonomous control and better yet, the write string/s do not save so you have to re-enter the data each time the vi is loaded up.

[Dennis_Knutson · Accepted solution]

There are numerous numeric to string conversion functions and you should learn to use one of the basic LabVIEW elements called a shift register. I can't save anything to version 6.1 so I hope the image below will help you get started.

 

Message Edited by Dennis Knutson on 03-30-2009 09:09 PM

[ms1]

Thanks. it works very well.