[micromanipulator6000] Traixial to coaxial adapters ...

John Shott shott at stanford.edu
Thu May 23 14:33:10 PDT 2013

Micromaniuplator community:

At some time in the past, someone has replaced our original coaxial to 
triaxial adapters with the version that is supplied in Physics Stores.  
Let me explain why this is not a good thing to use with this device and 
why I have replaced it with the more expensive Trompeter ADBJ20-E2-PL75 

In a coaxial to triaxial converter, there is the question (and option) 
of what to do with the driven guard signal (which is the portion that 
surrounds the actual signal line but is inside the outermost ground 
signal.  In the case of the adapters that they sell at Physics Stores, 
the driven guard is shorted to the outer grougd.  While this is probably 
OK for a CV measurement, it is bad for the SMUs if they are ever 
connected to one of these because that means that the driven guard can 
NEVER be driven to a voltage level that matches that of the signal.

The Trompeter ADBJ20-E2-PL75 simply leaves the driven guard portion of 
the triaxial cable floating.  This is preferred if you are ever hoping 
to connect one of the SMUs to a coaxial adapter ... which is often 
required, for example, if you want to connect a SMU to the chuck of the 

I have revoved the other coaxial to triaxial adapters and replaced them 
with the preferred Trompeter ADBJ20-E2-PL75 units.

I certainly hope that they do not leave this area.



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