Lock-in measurement, signal-unlock from 33220A

[Code]

Hi, has anyone accountered similiar problem in lock-in measurements? I have a combon of SR 830 DSP lock-in amplifier and Agilent 33220A function generator. 

The instruments work fine at manual control mode. However, when I tried to sweep frequency in 33220A, the signal was unlocked in SR 830 at each frequency point. I debug the code and find the unlock happened when the 33220A subvi execute "write visa". (See my attached diagram). If I use function generator knob to tune the frequency, it does not happen. Can anyone give a good explaination what may be happening? Is there a way to solve the problem?

Thanks.

Richard  

Message Edited by Code on 02-20-2006 02:44 PM

[Matt_S.]

Hi Code,

I'm a little confused about the setup you have here. I guess the best thing would be to send a description of how these devices are all connected. Are you using GPIB or RS-232?

 If you're sending commands to the 33220A directly, you should be seeing any changes in the setup of the SR830. The image you posted is just showing a setup for the string that's going to be sent  to which ever device the VISA session is associated with. If this is going to the 33220A, it shouldn't change any setting on the 830. I may just be confused of the setup on this lock-in amplifier.

There may also be a difference in how the 33220A handles the software frequency sweep and the sweep caused by using the knob to change the frequency.

 

Regards,
Matt S.

Message Edited by Matt_S. on 02-21-2006 03:13 PM

[Code]

Hi Matt,

Thank you very much for the help. I am using GPIB for both SR830 and 33220A. The labview diagram I attached is the subvi of how 33220A changes frequency.

The reference signal of SR830 is taken from 33220A SYNC TTL signal. The purpose is to detect output signal of circuit that is phase locked to the input signal from 33220A. There is no problem if I tune the knob to change the function generator frequency. However, if I use labview program, the signal is unlocked the moment data writes to 33220A. It could be a general problem of function generator.

Richard 

[Matt_S.]

Hi Code,

I would get in touch with Agilent and see if they know why it would be causing you this headaches. There is certainly nothing in the LabVIEW command you're doing that should cause this. It should only be communicating with the Agilent 33220A. Perhaps the 33220A is having a hard time queueing up the sweep and sending out the required signals to keep everything  locked.

If we can be any more help here, please let me know.

Regards,
Matt S.