[micromanipulator6000] Traixial to coaxial adapters ...
shott at stanford.edu
Thu May 23 14:33:10 PDT 2013
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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