measuring negative dB with picolog and picoscope

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Sa'ed Abu-Alhaija

measuring negative dB with picolog and picoscope

Post by Sa'ed Abu-Alhaija » Tue Nov 09, 2004 11:19 am

hi,
I am trying to measure negative dB using picolog and picscope. In theory, I should be able to measure (-80dB-10dB).
Do I need the "special" version of ADC-11 to be able to do that?! I have the standard version which, unfortunately, I cannot use directly to measure negative voltage as well.
I would be grateful if you let me know what i should do.
Thank you very much.
Sa'ed

Sarah

Post by Sarah » Tue Nov 09, 2004 12:29 pm

Hi

Thank you for your post.

To measure negative dB you are not necessarily measuring negative voltage. Therefore you should be able to use your existing ADC-11.

If you wish to measure negative voltages as well, then you will need the modified unit.

Hope this helps

Best Regards

Sa'ed

Post by Sa'ed » Wed Nov 10, 2004 2:11 pm

hello,
thank you for your reply. for some reason, i can see now the negative dB on picolog and picoscope. there must have been something wrong with my settings or computer :roll:
cheers
sa'ed

Sa'ed

Post by Sa'ed » Wed Nov 10, 2004 2:43 pm

hi again,
sorry to keep bothering you. i think i have found what prevented me from seeing the negative dB before.
i am using picolog R5.10.03. i can measure negative dB when the smaple interval is 1 second or more. as soon as i change the sample interval to be 999ms or less, i get the wrong readings with 0 being the min.
i would really appreciate any help from you.
thanks
sa'ed

Sarah

Post by Sarah » Thu Nov 11, 2004 10:30 am

Hi

I would suggest trying our latest software version which is R5.11.06. This is more up to date and the problem that you are seeing may have already been fixed. If you find that it has not, then please let us know so that we can investigate it further.

Hope this helps

Best Regards

Sa'ed

Post by Sa'ed » Thu Nov 11, 2004 12:02 pm

hi,
thanks for your reply. i have downloaded the latest version which is a lot faster, but i am still getting the same problem. as soon as the sample interval is less than 1 second, i lose the negative dB readings and they get replaced by random numbers between 0 and 1.
is there any chance that someone else could try to take some negative dB measurements, selecting 1-999ms as the sample interval, just to see if it is a common problem?
thanks again
sa'ed

Sarah

Post by Sarah » Fri Nov 12, 2004 9:33 am

Hi

I am sorry to hear that you are still having this problem.

Could you send us a .plw file to tech@picotech.com which shows what you are seeing? We can then use your same settings to try and recreate the problem and investigate it further.

Best Regards

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