[Halld-cal] [New Logentry] BCAL fADC pedestal data with detector off

[Chris Cuevas]

All,

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.

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.

Great to see the DAq running stable for 22 hours!

-Chris
~~~~~~~~~~~
On 5/8/2014 2:25 PM, dalton at jlab.org wrote:
>
>
>   BCAL fADC pedestal data with detector off
>   <https://logbooks.jlab.org/entry/3285753>
>
> Lognumber 3285753 <https://logbooks.jlab.org/entry/3285753>. Submitted 
> by dalton <https://logbooks.jlab.org/user/dalton> on Thu, 05/08/2014 - 
> 14:22.
>
> Logbooks: 	HDBCAL <https://logbooks.jlab.org/book/hdbcal> HDLOG 
> <https://logbooks.jlab.org/book/hdlog>
> Tags: 	DAQ <https://logbooks.jlab.org/tag/daq>
> Entry Makers: 	dalton
> References: 	3285542 - BCAL pedestals monitored overnight again 
> <https://logbooks.jlab.org/entry/3285542>
> 3285334 - BCAL pedestals monitored overnight 
> <https://logbooks.jlab.org/entry/3285334>
>
> 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.
>
> 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.
>
> 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.
>
>
>
> _______________________________________________
> Halld-cal mailing list
> Halld-cal at jlab.org
> https://mailman.jlab.org/mailman/listinfo/halld-cal

-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://mailman.jlab.org/pipermail/halld-cal/attachments/20140508/66cf825a/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 328406 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/halld-cal/attachments/20140508/66cf825a/attachment-0005.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 15965 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/halld-cal/attachments/20140508/66cf825a/attachment-0006.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 16470 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/halld-cal/attachments/20140508/66cf825a/attachment-0007.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 16185 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/halld-cal/attachments/20140508/66cf825a/attachment-0008.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 324829 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/halld-cal/attachments/20140508/66cf825a/attachment-0009.png