McAfee causes DAQ misread

[verdmonte]

We have been running production s/w with Labview 8.6 for some time (4 years). We are using a PXI 6071E with Traditional DAQ drivers.  Recently we discovered that during a long 5 minute DAQ read of an Analog Input we would get an incorrect read.  There was no error recorded from the DAQ but you could see that intermittently the DAQ read would start showing pulses where a steady voltage should have been.  This would be very intermittent maybe once out of 50 runs (we run 24/7).  We are sampling at a very low rate of 20 samples per second.  After many attempts at modifying the configuration of the DAQ we disabled McAfee and have not seen the problem in over two weeks.  We suspect that due to the fact that the DAQ uses a very high CPU processing time and that McAfee can also hog the CPU periodically that when this happened that it interrupted the DAQ.

[Zach J]

Hello verdmonte,

With your Analog Input task, were you using the Windows system clock to peform the acquisition or were you using the hardware sample clock on your PXI-6071 E?  With the Windows system clock, acquisition can be less than deterministic, meaning cycle times can vary by up to 10ms.  If McAfee was running a scan during an acquisition, this could lead to large lag times using the Windows system clock for acquisition.  With a hardware sample clock, this would be unexpected.  If you are unsure which you are using, post a screenshot of your code and I may be able to offer some suggestions to keep this from occurring again.  In the mean time, I would also suggest disabling McAfee while you take your acquisitions.