Agilent 33250A manual sweep (1Hz steps)

[juliantuilmenau]

Hi,

I am trying to do a manual frequency sweep using the standard waveform vi and incrementing the Hz count. The vi basically sends the following VISA write commands to the agilent 33250A via GPIB:

FUNC:SHAP SIN;:VOLT:UNIT VPP;:FREQ 1000.000000;:VOLT 1.000000;:VOLT:OFFS 0.000000;
FUNC:SHAP SIN;:VOLT:UNIT VPP;:FREQ 1001.000000;:VOLT 1.000000;:VOLT:OFFS 0.000000;
FUNC:SHAP SIN;:VOLT:UNIT VPP;:FREQ 1002.000000;:VOLT 1.000000;:VOLT:OFFS 0.000000;
FUNC:SHAP SIN;:VOLT:UNIT VPP;:FREQ 1003.000000;:VOLT 1.000000;:VOLT:OFFS 0.000000;

The problem is that upon every command received, the agilent 33250a sends a ramp signal on the output port of 1mV for 0.05secs. As I am trying to find the resonance frequency of an externally driven resonating body, this additional noise is unwanted. In the attachments you can see the peaks up close, a resonating curve with the peaks when controlling the 33250a by software, and a resonating curve when simply turning its knob. 

Is there a better way to control the 33250a or a way to turn of these peaks ? The sweep function has been tried but not found accurate enough.

Thanks alot in advance,

Julian

[Dennis_Knutson]

This might be a question better asked of Agilent tech support. There are some things that you could try yourself. Experiment with variations of the command. Look up the syntax in the manual. Perhaps part of the entire command causes the instrument to briefly switch on/off. See if you can send just the frequency command.

[Albert.Geven]

You might try to send only the frequency part of the command after the first command.

Now you are telling the instrument to start anew.

So try as second line

:FREQ 1001.000000;

good luck

[Henrik_Volkers]

Another idea from another thread: you can use an analog output and the modulation input of the generator to shift the frequence. Together with a phase measure you can build up a quite fast control loop.

[juliantuilmenau]

Sending out only the :FREQ command worked. I thought that I tried that before with no luck, sometimes you really should give it another shot 🙂

Thanks alot everyone!