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Spectrum display with delayed trigger

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Spectrum display with delayed trigger

Postby CoyoteDavid » Sun Feb 11, 2007 8:23 am

The Spectrum display seem to be wrong if the trigger delay is set to -50%. I seem to get all the frequencies doubled. If I set the tirgger point to 0%, it looks OK. Is this normal?
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Postby Sarah » Tue Feb 27, 2007 11:03 am

Hi

What scope are you using and which revision of software? I have tried this and cannot see a problem. It would be helpful if I can try the exact same setup as you are using to see if the software is at fault.

Best Regards
Sarah
 

Postby CoyoteDavid » Wed Feb 28, 2007 6:45 am

Hi Sarah,
Attached are two PSD files, and two image files showing the problem I see. One shows a noisy 10 KHz square wave, the other shows a very clean 1 KHz square wave. Notice the spectrum displays. If you leave the display refreshing long enough, occassionally it will show the correct spectrum for a single trace, then switches back to the one I captured. It is almost always showing the display I captured.
-David
Attachments
2007_02_27_Pico2105_Spectrum_Offset_1KHz.PNG
Spectrum offset with 1 KHz sq wave
(41.17 KiB) Downloaded 1421 times
2007_02_27_Pico2105_Spectrum_Offset.PNG
Spectrum offset with 10 KHz square wave
(44.35 KiB) Downloaded 1414 times
2007_02_27_001_Pico2105_Spectrum_Offset.psd
Spectrum offset with 10 KHz square wave
(25.01 KiB) Downloaded 258 times
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Postby Sarah » Wed Feb 28, 2007 3:11 pm

Hi

I have tried this out using a 2105, the latest software and your file that you supplied (as well as setting up on my own) and all the results I get are normal.

What version of the software are you using? If it is not 5.15.6 then I recommend downloading this from our website.

Best Regards
Sarah
 

Postby CoyoteDavid » Thu Mar 01, 2007 8:51 pm

I am running 5.15.6. I have tried it on two systems, with the same results both times. When I do Help-->About, I get the following:

Release 5.15.6 - 32 bit
Driver Version: 1, 7, 0, 2
USB Version: 2.0
Hardware Version: 4
Hardware Model: 2105
Serial Number: JAL82/78
Calibration Date: 20Nov06
Error Code: 0
picopp.sys Version: 1.12

Some more data points:
If I set the trigger to -25%, the display goes to showing a 1 KHz signal with a peak at 4 KHz (4 times the correct value). If I set the trigger to -10%, the spectrum shows the peak at 10 KHz (10 times the correct value). At -5%, it shows up at 20 KHz, at -1%, it shows up at 100 KHz, etc. This pattern seems to follow for all values in between, till the trigger is at zero, (at zero the spectrum is OK). In all cases, it is flashing between being correct and the wrong setting, with the wrong setting showing about 70% to 80% of the time.

Given the apparant resolution on the spectrum display, my guess is that it is actually correct data, but the display routine is stretching it out and only showing the first 10% of the real data that was calculated (in the case of the -10% trigger). Also, in all these tests, the scope display looks normal.

I have included a snapshot and psd file for the -10% case.

Thanks,
-David
Attachments
2007_03_01_001_Pico2105_Spectrum_10percent.psd
psd file for Pcio 2105 with trigger at -10%
(24.11 KiB) Downloaded 283 times
2007_03_01_001_Pico2105_Spectrum_10percent.PNG
Spectrum on 2105 with trigger at -10%
(41.8 KiB) Downloaded 1364 times
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Postby ziko » Thu Mar 08, 2007 6:43 pm

Hi I have recreated what you were doing, and this is a bug in our software, I have registered this as a bug, thank you for your input.
Ziko

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