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digital out prop delay

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#1 ElectroLund

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Posted 15 July 2013 - 09:21 AM

Hello, I'm using a U3 in a system that has a pretty tight requirement for the propagation delay.  I am measuring this propagation between a digital input on one LJ channel, my LabWindows software reading this state and then setting a different LJ digital output channel.


It is important in my application that this delta be in the low miliseconds, but I am measuring anywhere from 5 to 25ms on a very fast Windows 7 desktop.  On another slower Windows XP machine, this same experiment runs as slowly as +100ms.


I have found a few threads here that are similar to what I'm after, but not exactly.  I am wondering if this is purely the fault of the interface between the LJ and my target PCs, and the Nation Instruments software running on that target PC?  I realize there's a lot of overhead between points A to B.  But was just curious if there are low level settings that I should be configuring at the LJ level.





Attached File  Gregs desktop - best case.BMP   300.05KB   941 downloads


Attached File  Gregs desktop - worst case.BMP   300.05KB   940 downloads

#2 LabJack Support

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Posted 15 July 2013 - 04:56 PM

The first thing I would do is see if you can confirm the 600us command/response time you expect from Section 3.1 of the U3 User's Guide.  You can use the U3_AllIO example from the VC6_LJUD archive, and set numChannels=0 so it does not do any analog inputs.

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