This is something I've wondered about for quite a while and even after combing through some HP and Agilent manuals, I still don't have the exact answer. On a lot of impedance analyzers and RLC meters, I'll see BNC connectors on the front panel that are marked "U+ U- I+ I-" or more commonly "Hcur Lcur Hpot Lpot." I'm sure this refers to differential voltage and current-sensing amplifiers inside the instrument but I had a few questions about that...
- Why are there four inputs and a ground (vs maybe just one or two inputs, plus ground)?
- Is there a name for this "architecture?"
- Has anyone come across a full schematic of this input "architecture?" (I have only found summaries)