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Extreme Noise Triggering O-scope

Question asked by jlking_bah on Jun 28, 2017
Latest reply on Jun 29, 2017 by jlking_bah

Unit: MSO-X 4154A

O-scope is not connected to DUT.  BNCs are floating (no shorts on hand).  Signal generator option was 50 ohm terminated and unterminated when problem was seen.

 

Background:

A few weeks ago (early June), went to a different site to collaborate with a new group on some hardware development.  I took my o-scope with me as I have been using it as my means of recording RF waveforms in case I needed to perform sanity checking.  I kept seeing extreme noise triggering my scope (example cell phone photo):

 

Noise triggering at off site

I then returned to my office and no longer saw the issue.  In fact, for months prior, I did not see the issue.

 

My employer moved to a new office and I have been re-establishing my lab at the new location.  Today, another in my lab saw this behavior with the o-scope.  I took several photos, disconnected our DUT, switched inputs back to 1M probes (not connected) instead of the 50 ohm BNC cables we typically work with, and saw the problem multiple times:

New office false triggering

 

So, is this earth ground with extreme bouncing?  Is this something going on in the scope?  How to I solve/mitigate this?  This is causing us to trigger at the wrong time because we're triggering on this issue instead of the RF we're trying to capture.

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