[Halld-controls] Type J Thermocouples in the CDC

Fri Mar 9 09:45:46 EST 2012

I will inject my two cents. _Disclaimer:_ This is not to discount 
anyones opinion or to inflame its just to offer another viewpoint.
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.

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.

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.

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.

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.

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.

For what its worth.
JC

On 3/9/2012 8:13 AM, Joshua Ballard wrote:
> 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:
>> 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.
>>
>> http://www.omega.com/DAS/pdf/D5000.pdf
>>
>> Hovanes.
>>
>>
>> On 03/08/2012 04:39 PM, Joshua Ballard wrote:
>>> 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
>>> _______________________________________________
>>> Halld-controls mailing list
>>> Halld-controls at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/halld-controls
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-- 
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

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