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Intermittent temperature readings

I am running Fieldpoint modules, but believe that the problem is actually with the LabVIEW code.  The larger version of this program(this is the simplified time critical loop) worked fine for about 3 months, then recently the TC-120 modules have been timing out intermittently.  I am running the Fieldpoint 2015 control module, 6 TC-120's, and 2 RLY-420's.  Modules 3 through 6 have been timing out intermittently(all 8 thermocouples of whichever module times out).  The problem is temporarily fixed by lifting the TC-120 from its base and putting it back into position(cycling power).  Connections are sound and timeout only occurs when the LabVIEW program is running.  Cold junction temperature is well within suggested range.  I have 6 TC-120 modules because the larger version of the program has to take many more temperatures.  I have simplified the program(attatched) to try and diagnose the problem, but it keeps occuring.  Any help or suggestions would be very much appreciated.
 
Summary of Program:  This program turns an oven on when the average of 8 simultaneous temperature measurements is below 150F.  The oven is turned on via RLY-420 switching common on a contactor.  The oven is to run for 12 seconds.  This program executes four times. 
 
Thanks for the help,
Chris
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Try slamming the modules together really hard--and I'm not kidding. The original FP systems are famous (or infamous) for connection problems between modules that manifest in just this way. You didn't mention the environment the modules are installed in, but the original FP is very sensitive to shock and vibration. I have one customer that has a rail of 5 or 6 modules with a bungee cord wrapped around the whole thing to keep the modules smushed together.

Alternately, if you don't care for bungee cords, I've always liked Opto22...

Mike...


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Or you can change to cFP. These units are much more reliable. We have upgraded all our systems from std FP to cFP and now have no reliability problems.
You could also try swapping modules in their bases to see if those which timeout are faulty, or wether it is just your connections.

Message Edited by DavidT on 08-25-2005 05:45 PM

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