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RPM Signal On Veristand

I removed the RPM signal and







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Message 11 of 16

Sorry no info


I removed the RPM signal and th HP loop count had dropped considerably


lp hp rate.png


The RPM input signal is the only signal I have. 

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Message 12 of 16

Hi Tim,


You mentioned earlier that you were using a CompactDAQ chassis. Because this chassis is connected over USB I think it's possible that accessing your counter channel through multiple driver layers is taking longer than your 1ms target period. USB is not a deterministic communication method and some jitter is inevitable. You may need to reduce your target control loop frequency considerably in order to sample channels through your cDAQ chassis. 


It may be possible to work around this by using a Custom Device. Is your primary control loop rate flexible or do you need a 1ms period for some requirement?




Andy C.

Applications Engineer

National Instruments

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Message 13 of 16

Yes I was using a cDAQ chassis but I have switch over to a PXI chassis which I am communicating with a 8360 MXI Express card.


I get the same result with an update rate of 1 Hz to my RPM signal.  When I create a task in MAX the update rate is substancially faster using the same hardware which leads me to believe something in Veristand is slowing this signal refresh rate down. 


My primary control loop is flexible.



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Message 14 of 16

Can you (or have you) feed a faster signal (e.g. 5 khz) into your RPM input and check Veristand's rates?

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Message 15 of 16

I would need some sort of  signal generator to send in a signal of that speed.


The overall system performance is poor.


I tried a simple loop back test where I would output a 0-10V signal from my AO.  I tried reading this signal from an AI channel and I cannot even get the system to deploy.  It appears the overall system performance with windows is rediculously poor and had I known this I would of went with a different configuration.



I mean trying to use 2 channels at 100 Hz causes a deployment failure?  This is very poor!



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Message 16 of 16