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I will inject my two cents. <u>Disclaimer:</u> This is not to
discount anyones opinion or to inflame its just to offer another
viewpoint. <br>
I have built, operated, and maintained a lot of control systems over
the last 25+ years, which have to run 24/7/365, and a few truths
always float to the top.<br>
<br>
1. The control system is not the experiment. It should work, it
should be easy to operate, and it will always break in the middle of
the night when people are not available so it should be easily
maintainable.<br>
<br>
2. Make it robust and use industrial components where ever possible
because they are designed for continuous operation in less than
ideal environments. If you dont you might be working on it a lot
during operation. Lab grade is not the same as industrial grade.
Industrial grade is what is used in all manufacturing plants where
they cannot afford down time. <br>
<br>
3. Stay away from specialized pieces of hardware available from
discount vendors. They may not have the longevity of available
replacements that main-steam hardware vendors provide. This might
precipitate the need for more wiring adaptations and modifications
to specialized code/devices along the way as replacement components
become unavailable.<br>
<br>
4A. Try to stick with one standard base of hardware across your
system when possible. This makes the wiring and programming for all
devices similar. If you dont you will be searching for the manual to
one unique piece of hardware in the middle of the night when it when
it breaks. It makes care and feeding more straight forward.<br>
<br>
4B. By sticking with one standard base you also make it easier for
follow on techs and programmers to take care of the system because
it minimizes, or eliminates, the writing of small pieces of
specialized code that make special pieces of hardware function.<br>
<br>
For what its worth.<br>
JC<br>
<br>
<br>
<br>
On 3/9/2012 8:13 AM, Joshua Ballard wrote:
<blockquote cite="mid:4F5A01F4.2010702@jlab.org" type="cite">
<pre wrap="">The Omega devices are $65 per channel (4 channels) - we'd need 3 of
these devices plus 3 serial to EPICS interfaces (I don't know what these
would be, or what they would cost). And then we'd need to spend the
money for you to program them.
If we went the Allen Bradley route, it would take 5 minutes to configure
the modules and assign aliases to the hardware tags and they'd
immediately be available to EPICS. Additionally, the Allen Bradley
stuff is made for industrial environments in which case our
maintenance/repair costs would be next to nothing.
I tend to think the lifetime cost of the Allen Bradley solution is lower.
On 3/8/2012 6:09 PM, Hovanes Egiyan wrote:
</pre>
<blockquote type="cite">
<pre wrap="">I am not sure if it is the least expensive way, but I think it would
be the best to use Omega RS232/RS485 interface devices with their
thermocouples.
The programming of the serial for their devices for monitoring can be
pretty easy;
I have not done it myself, but Krister from Hall B told me that those
he has are pretty
simple modules.
<a class="moz-txt-link-freetext" href="http://www.omega.com/DAS/pdf/D5000.pdf">http://www.omega.com/DAS/pdf/D5000.pdf</a>
Hovanes.
On 03/08/2012 04:39 PM, Joshua Ballard wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hello,
CMU plans to purchase 10, Type J thermocouples for the CDC. I was asked
to determine the best way to get the signals into the PLC and EPICS.
Option 1: ControlLogix thermocouple module. The 1756-IT6I2 is a 6
channel, Cold Junction Compensated (CJC) thermocouple input module. The
price per channel is $256. In this case, the thermocouple leads would
need to be routed from the CDC all the way over to the solenoid controls
rack. I believe thermocouple wire and connectors are "cheap", so this
shouldn't be a problem.
Option 2: Point I/O thermocouple module. The 1734-IT2I is a 2 channel,
CJC thermocouple input module. The price per channel is $161. We
currently have a Point I/O "chassis" installed in the solenoid controls
rack and, again, we'd have to run thermocouple wire from the CDC to the
solenoid controls rack. That is, unless we anticipate additional
thermocouple channels for the other detectors, in which case it may be
advantageous to buy another "chassis" and install it closer to the magnet.
The only reason to bring the thermocouples into the PLC is to get the
values into EPICS. The cost per channel for the Point I/O system seems
comparable to Omega thermocouple controllers AND the PLC and EPICS
programming would be minimal.
So, unless somebody knows a better way to get thermocouple data into
EPICS, my recommendation is that we use Point I/O.
Josh
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<br>
<pre class="moz-signature" cols="72">--
Jonathan Creel
Cryogenics, Electrical Power and Control Systems Team Supervisor
Thomas Jefferson National Accelerator Facility
12000 Jefferson Avenue, Newport News, Virginia, 23602
Phone (757)269-5925</pre>
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