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Hi Brian,<br>
I appreciate you looking at the algorithm. The algorithm you
suggest was used for a time. It caused the current to be
recalculated every loop and made the temperature less stable. One
of the engineers asked that the current only be changed when the
power dissipation was out of the range that Lakeshore recommends for
Cernox operation. I am curious as to why the existing algorithm
only works when temperature is increased. Could it be that more
power is dissipated and the current is recalculated? Why does it
not work when temperature is decreased? Could it be that power
dissipated is within range and current stays constant.<br>
<br>
I will need Rubens permission to make the change.<br>
<br>
As for additional power checks, the algorithm below matches the
latest flowchart see attachment v1. I do not see additional power
checks. I may have sent you an older copy of the flow chart which
did have additional power checks see attachment v0. The engineers
asked me to change the code to what you see below. <br>
<br>
I can apply your suggested algorithm, but everyone will need to be
aware that the temperatures will not be as stable as they are now
with the fixed currents. <br>
<br>
I think we need to look at another parameter before recalculating
the current, maybe voltage? Lakeshore recommends that the voltage
across the RTD be 10mV or less for the full range of temperatures
that the Torus operates. <br>
<br>
What are your thoughts on this?<br>
Christiana<br>
<br>
<br>
<div class="moz-cite-prefix">On 10/14/2016 12:27 PM, Brian Eng
wrote:<br>
</div>
<blockquote cite="mid:74B6A81D-3DF1-47B3-92B5-D40C942E3A4D@jlab.org"
type="cite">
<meta http-equiv="Context-Type" content="text/html;
charset=us-ascii">
Instead of explaining with text, which could be confusing, I've
attached a few screenshots of the various VI block diagrams.
<div class=""><br class="">
</div>
<div class="">For reference here's a PDF for the
algorithm: M:\hallb_eng\CLAS12\Magnets\Torus\JLab
Torus\C&I_Torus\Controls_&_Wiring\Fast DAQ\Cernox
Algorithm\TR Algorithm.pdf</div>
<div class=""><br class="">
</div>
<div class="">Here's what the VI looks like now (attached as
current.png):</div>
<div class=""><br class="">
</div>
<div class=""><img id="0C0319D7-0C88-4621-B1D6-353833916B27"
src="cid:part1.4AF7EEC0.D3EDD120@jlab.org" class=""
height="409" width="590"></div>
<div class=""><br class="">
</div>
<div class="">The issue I've found with the current algorithm is
that it will increase the current as the temperature increases,
but it won't decrease the current as it goes down.</div>
<div class=""><br class="">
</div>
<div class="">After noticing that the logic doesn't exactly match
the reference algorithm (namely the additional checks on power
dissipation) I modified the VI to look like the following
(attached as updated.png):</div>
<div class=""><br class="">
</div>
<div class=""><img id="19191C65-11E8-47B9-9EA7-EE00895C906F"
src="cid:part2.8C49DCEF.E5350690@jlab.org" class=""
height="364" width="588"></div>
<div class=""><br class="">
</div>
<div class="">This version properly increased and decreased the
current with my admittedly limited testing of using a single
potentiometer in place of a cernox sensor and varying it up and
down between 4K and 325K.</div>
<div class=""><br class="">
</div>
<div class="">Finally I removed some of the terminals that weren't
being used and changed the code to use more LabVIEW primitives
in my process of upgrading to 2016 (attached as simplified.png):</div>
<div class=""><br class="">
</div>
<div class=""><img id="63DBAD13-037A-4AB8-8C5C-CB7F8E129CD5"
src="cid:part3.831686BD.3AC7BA07@jlab.org" class=""
height="208" width="577"></div>
<div class="">Hopefully the images make sense and get sent through
to the mailing list okay.</div>
<div class=""><br class="">
<div class="">--<br class="">
Brian Eng<br class="">
Detector Support Group<br class="">
757-269-6018</div>
<br class="">
<blockquote type="cite" class="">On Oct 12, 2016, at 6:44 PM,
Amrit Yegneswaran <<a moz-do-not-send="true"
href="mailto:yeg@jlab.org" class="">yeg@jlab.org</a>>
wrote:<br class="">
<br class="">
hello brian,<br class="">
<br class="">
today you and i had a discussion about the cernox sensor
problem.<br class="">
at the dsg meeting we further discussed the matter.<br
class="">
you mentioned that there were some errors in the main
program VIs, which i'vent seen.<br class="">
when you mentioned that you had e-mailed christians (author of
the code) and nick i mentioned you to post a few words
regarding this issue, so that rather than a select few, all of
us including i might be aware of the source and cure.<br
class="">
perhaps it slipped your mind that i requested you the source
and the cure for the problem.<br class="">
i am documenting all these issues so that newcomers like pablo
and tyler understand these issues and can provide <br class="">
effective support.<br class="">
<br class="">
so when you come back on friday please do so.<br class="">
amrit</blockquote>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
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</blockquote>
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