User name R. Michaels
Log entry time 14:52:38 on July25,2007
Entry number 208727
keyword=raster current pickoff issuesReminder: an amplifier adjusts the raster pickoff current to fit
into our ADCs.
There was a problem that the signals going to the ADCs had ripples
(oscillations) leading to spikes in the current distribution.
C. Cuevas and I checked the amplifier boxes; they are fine -- fast
enough and no problems. We found that the oscillations occur
because the long RG58 cables have a ringing response. It is
very small and difficult to see prior to putting into the amplifers,
but the amplifiers sense it and make a larger oscillation.
The trick to reduce this is to put the amplifiers downstairs BEFORE
the long cable run. (Cannot do this for BPM signals, they would
be too small). Doing this gives results like Fig 1 and 2 for
X and Y. This is similar quality to what we used in e06007 (nothing
new really).
There was some speculation we could do better with RG8 or other
fatter cables.
In the past we read these data in a VME crate near the beamline.
But we got rid of that crate in 2003 (it was slow and always had
to be rebooted).
Also note, the derivative signals were removed because I needed
a slot and nobody was using those data anyway, I think.
FIGURE 1
FIGURE 2
