One More Fix

[Tom Droege <tdroege@veriomail.com>]

I am trying one more fix for the bad data problem.  Sigh!  Every thing I do 
makes the problem go away.  It is very hard to tell if I have made an 
improvement.  But there is hope.

It is sort of like have a theory about how planets are formed.  Lots of 
theories say planets can't form.  So one works on the theories until you 
figure out one that sometimes lets planets form.  Then you debate how 
frequent sometimes is.

With my problem, things tend to go bezark late at night when I am not 
watching.  If I drag the oscilloscope up to look at all the test points, 
the problem stops when I attach a probe.  Sigh!  I though it was a high 
frequency oscillation in the signal chain.  My present theory is 
motorboating in the TEC control loop.

I have designed a fix which will stop motorboating if it exists.  What is 
motorboating?  This is a particular type of relaxation oscillation caused 
by feedback through the power supply.  Seldom seen today with differential 
amplifier circuits.  It was called motorboating because of the sound it 
made in an amplifier system.

I have the fix installed in TOM and MIKE.  We shall see.

Tom Droege