[Halld-controls] Type J Thermocouples in the CDC

[Joshua Ballard]

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