Larry wrote:


At this level, a lot of what the Keithley is measuring is the diode's own
generated voltage. Hook the Keithley to a silicon diode sitting on the
bench, not attached to anything. Depending on how hot it is (and how close
to any radioactivity it is), there's always a junction voltage from the
thermionic emission of the junction, itself.


Indeed! Actually the junction voltage
was ~50 millivolts so I "tuned it out"
as they say.

Got a hot radioactive source around? Keep the Keithley across the diode
and move the diode up against any beta or gamma sources and watch it fly...
(c;

(Depleted uranium bullets are great for this experiment. They're free in
Afghanistan and Iraq...)

I could try a smoke detector or Coleman
lantern mantle with thorium, I guess.
I'll pass on the DU though.


Which Keithley is it? I used to repair and cal them at the Metrology
Laboratory of the Quality Assurance Office, Charleston Naval Shipyard (Code
132)...may she rest in peace.



It's a 610B with electrometer tubes.
Works amazingly well for its age. It
does have a personality as you know.

Chuck

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