From: lugnut808@spam.yahoo.com   
      
   On 16/08/2023 12:42 am, Bob Engelhardt wrote:   
   > I'd like to use both traces on my scope to look at 2 voltages that are   
   > without a common reference.  E.g., across R1 & across R3:   
   >   
   > ________R1____   
   >      |   
   >      R2           ...   
   >      |   
   >      R3   
   > ____|______   
   >   
   > I know that there are isolation probes to do this ($$$), but I'm   
   > wondering if there is some clever other way to do it.  In my minimal   
   > experience I can't see one, but I'm hopeful that someone more clever   
   > than I has one to share.   
   >   
   > Thanks, Bob   
      
      
   You could buy or build a differential probe.   
      
   If you only wanted to see one trace (e.g. the voltage across R1), you   
   could put the scope into summing mode and invert one channel. This   
   doesn't work all that well because the gain of the two channels and   
   probes isn't all that well matched.   
      
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