PROBLEMS ACQUIRING WAVEFORMS FROM TEKTRONIX 220 (TDS220)

[ricmail85]

Hi,

I'm building a DAQ system as it follows:

1. A TDS220 oscilloscope that acquire signals from MPPC sensors.
2. A PC, connected with RS-232 to the TDS220, that save the waveforms acquired by TDS.
3. On the PC a Labview program (based on the Example2.vi subprogram, included in the TDS220 drivers).

The problem I noted is: when the waveform goes through the 0 value (for example a curve growing from -5 to +5), the program generates an error (I see it come from the VISA READ.vi). Instead, If the waveform's values are all positive or all negative, then the program doesn't report errors. Provisionally I'm working with only "half display" of the TDS (ie a all positive or all negative range); to do this, I introduced an OFFSET on the Amplitudes.

Can you help me?

Thanks.

[Dennis_Knutson]

What kind of error are you getting? When you get the error, has the scope triggered and captured a signal? VISA and LabVIEW don't care one bit if the waveform crosses the 0 point but you may not have programmed the scope correctly to do a capture.

[ricmail85]

 Hi, 

thanks for the reply. Now I'm not at the University, but I remember the error was like to "error... scan from string". If you wont, I can send you my labview project. What do you think I have to do? However the scope acquired and triggered correctly. Thanks a lot!

Message Edited by ricmail85 on 04-28-2009 05:46 PM

[LiciaP]

Hi,

please let us know when possible the exact error code, which could be useful to understand the problem.

If I understood correctly, your VI is modified based on the driver examples; but do the original examples work correctly?

You may also consider this forum post.

Bye!

Licia