crosstalk problem

[bert linten]

hey
i'm experiencing crosstalk when i use my program on a fielpoint cfp2020.
I'm using my fielpoint to regulate two valve's (must become 4. This must be at high speed.
But when i use one valve there don't seem te be a problem. When i use both the valve's there
seems to be a strange 'co-operation' between them both. they start to regulate really strange.
i've looked on the internet and found something about crosstalk but not what i can do about it.
can someone help????



grtz bert

[JorisV]

Hi Bert,

Cross-talk can be caused by inputs with a high source impedance or by floating sources. You can check out the links below

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

http://digital.ni.com/public.nsf/websearch/48CC15B99E99F87886256297005F69A8?OpenDocument

Now you are talking about high-speed? With a Fieldpoint? That seems strange since a Fieldpoint is limited to a 1 kHz PID loop maximum. You can hardly talk about high speed.

So, cross-talk is related to analog inputs and it don't think that this is the problem with your valves. I guess you are sending out a pulse train (FP-PWM) to your valves, so this is not a cross-talk related problem.

I would look inside your code first and check if the interference is not related to the written software. Maybe there is a problem with race conditions between local/global variables. Check if there is a common shared resource between the code for the two valves. Make sure that for example the first control loop is not locking a resource of the second control loop. If the two valves a working OK separately and it is not software related than maybe the problem is coming from the wiring?

That's all I can think of with the information I have.

Regards.

JV