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voltage buildup on some unconnected AI-112 terminals

Hi

I have this strange issue that some terminals tend to autobuildup voltage. And some doesn't.

Usually it doesn't bother me since the module is measuring correctly when I connect sensors. BUT the buildup goes up to the range limit of the module, 10.4V and generates errors. 

I have read the Knowledge Base 2XBC04Q2 but I'm not really happy with its solution. Would this mean that I have to connect a 100Ohm resistance to every channel? And why do some AI-112 modules show this behaviour while others don't.

 

Thank you for any help

Yves

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Hi Yves,

 

There is no isolation between channels on the AI-112. On the other hand, the cFP-AI-118 offers channel to channel isolation (750 Vrms) allowing each input to have a separate ground.

 

Therefore with your AI-112 it is expected that you get crosstalk, floating, or some other kind of unexpected voltage on your channels.

 

The following KnowledgeBase can give you some insights on reducing such unexpected signals:

 

http://digital.ni.com/public.nsf/allkb/B9BCDFD960C06B9186256A37007490CD?OpenDocument

 

Hope this helps,

Bart

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