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All,<br>
<br>
It looks like you are getting down to the intrinsic
resolution/accuracy of the 12bit ADC! I imagine if you completely
de-cabled one board per crate, the amplitude (rms) variation of each
channel would be very close to the datasheet specifications for the
equivalent number of bits(ENOB) and integral non-linearity(INL) of
+/- 1 ADC count. There are a few other components in the ADC
circuit that have temperature dependencies, and I am still a bit
puzzled as why there is a 15deg-F variation in the values of the VXS
crate temperature probes. Most likely the probes reading close to
90F are near the ROC slot, but that is an assumption. I know these
probes are not high accuracy, but I do not have a good explanation
of the 15deg-F variation within each crate assuming the air inlet
temperature is common.<br>
<br>
One 'knob' to turn is the crate cooling fan speed, and I noticed
last time I was in the hall that the speeds were set conservatively
lower than the max of 6000RPM. It will be a hot evening and the
HVAC will be working hard, and if a run were made with the fan speed
pushed a bit higher it may offer some insight.<br>
<br>
Great to see the DAq running stable for 22 hours!<br>
<br>
-Chris<br>
~~~~~~~~~~~<br>
<div class="moz-cite-prefix">On 5/8/2014 2:25 PM, <a class="moz-txt-link-abbreviated" href="mailto:dalton@jlab.org">dalton@jlab.org</a>
wrote:<br>
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<article id="node-358497" class="node node-logentry article
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<header class="node-header">
<h1 class="node-title" rel="nofollow"> <a
moz-do-not-send="true"
href="https://logbooks.jlab.org/entry/3285753"
rel="bookmark">BCAL fADC pedestal data with detector
off</a> </h1>
</header>
<div class="date-vitals">
<p class="author-datetime"> Lognumber <a
moz-do-not-send="true"
href="https://logbooks.jlab.org/entry/3285753"
class="lognumber" data-lognumber="3285753">3285753</a>.
Submitted by <a moz-do-not-send="true"
href="https://logbooks.jlab.org/user/dalton">dalton</a>
on <time datetime="2014-05-08T14:22:05-0400"
pubdate="pubdate">Thu, 05/08/2014 - 14:22</time>. </p>
<table class="field-vitals">
<tbody>
<tr>
<th>Logbooks: </th>
<td><a moz-do-not-send="true"
href="https://logbooks.jlab.org/book/hdbcal">HDBCAL</a>
<a moz-do-not-send="true"
href="https://logbooks.jlab.org/book/hdlog">HDLOG</a></td>
</tr>
<tr>
<th>Tags: </th>
<td><a moz-do-not-send="true"
href="https://logbooks.jlab.org/tag/daq">DAQ</a></td>
</tr>
<tr>
<th>Entry Makers: </th>
<td>dalton</td>
</tr>
<tr>
<th>References: </th>
<td><a moz-do-not-send="true"
href="https://logbooks.jlab.org/entry/3285542">3285542
- BCAL pedestals monitored overnight again</a><br>
<a moz-do-not-send="true"
href="https://logbooks.jlab.org/entry/3285334">3285334
- BCAL pedestals monitored overnight</a></td>
</tr>
</tbody>
</table>
</div>
<div class="logentry node-content">
<p>Pedestal data was taken in the BCAL north fADCs for 25
hours from 12:31 yesterday until 13:22 today with the
BCAL detectors powered off. The same type of time
dependent changes were observed (see Fig. 1) as previous
two evenings (referenced log entries). The distribution
of the differences in the average over time can be seen
in Fig. 2, with a most probable value for this time
period of ~1.5 channel change. </p>
<p>The changes track very well with the temperatures in
the crates, which can be seen in Figs. 3 through 5. I
find this to be very compelling evidence that the effect
is due to temperature changes on the fADC boards
themselves.</p>
<p>This time there are no glitching channels. The largest
change, of 4.36 ADC samples, was for roc 43, slot 5,
channel 14 - see Fig. 6.</p>
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<pre wrap="">_______________________________________________
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