Temperature correction at AI835A modules, use correct temperature from first module on next muduels
I'm using AI835A as remote IO coupled via CI840 (Profibus) versus
Melody controller PM877. Configuration is done via DTM.
On first module for correction a PT100 is used at 8th channel,
all other channels are set to "CJT measured via ch. 8".
Those measurements work fine.
For next modules I have sent the correction value via program from first module
to output channels on next modules. (sent same value as got from first module on channel 8, checked by debugging on profibus)
I have set channel 1..7 to "Remote cold junction comp".
In this case the temperature is measured around 50 degrees too low
Correct temp is 13 Cel, measured temp is -34Cel.
If I set to "Fix junction temperature" or "CJT measured via ch. 8" temperature
looks ok (even if nothing is connected to 8th channel of that module).
But I think then it works just with fix set dummy temperature.
So how correctly get correction temperature from first to next modules?
Melody controller PM877. Configuration is done via DTM.
On first module for correction a PT100 is used at 8th channel,
all other channels are set to "CJT measured via ch. 8".
Those measurements work fine.
For next modules I have sent the correction value via program from first module
to output channels on next modules. (sent same value as got from first module on channel 8, checked by debugging on profibus)
I have set channel 1..7 to "Remote cold junction comp".
In this case the temperature is measured around 50 degrees too low
Correct temp is 13 Cel, measured temp is -34Cel.
If I set to "Fix junction temperature" or "CJT measured via ch. 8" temperature
looks ok (even if nothing is connected to 8th channel of that module).
But I think then it works just with fix set dummy temperature.
So how correctly get correction temperature from first to next modules?
Asked 8 months ago
Answers
1
I would be happy to be wrong, but I don't think there's a way of doing this. When we've used these cards, we had an RTD on the eighth channel of each card.
Answered 8 months ago
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