GPS Clock(PPS) Vs PC clock stability

[GPGPR]

Hi,
 
I'm using a GPS pulse per second as a timing source for a timed-loop.
 
So the Timed loop iterate on each rising edge of the GPS PPS.
 
I record the PC time stamp for every iteration and here is what i observed:
 
There is a time drift from the PC time of about 1ms per minute.
 
Since i know that the GPS PPS is quite stable(µs), can i assume that the loop iteration based on the GPS Pulse has a better timing that the PC timestamp make me believe?
 
I'm on a PXI platform non-real-time.
 
Regards,
 
Guillaume

[Chris G in AE]

Guillaume,If you are using the GPS correctly, the loop timing should be more accurate than your PC's clock.  The 1 ms delay observed between your PC and the GPS time could be caused by a multitude of factors.  However, this is most likely due to the inaccurate clock on the PC.  In order for the GPS and PC clocks to be completely synchronized, the PC clock must update to the GPS signal.  If the clock is not updating at a small enough interval, the PC clock will drift away from the GPS clock.  Try adjusting the synchronization rate of the PC clock so that it updates more frequently if you'd like to see the PC and GPS clocks match up at the end of your loop. 

[a***@gmail.com]

Post by GPGPR
Hi,
 
I'm using a GPS pulse per second as a timing source for a timed-loop.
 
So the Timed loop iterate on each rising edge of the GPS PPS.
 
 
There is a time drift from the PC time of about 1ms per minute.
 
Since i know that the GPS PPS is quite stable(盜), can i assume that the loop iteration based on the GPS Pulse has a better timing that the PC timestamp make me believe?
 
I'm on a PXI platform non-real-time.
 
Regards,
 
Guillaume

I suspect that more than anything you need to be aware of interrupts going off and extending the timed loop when compared to the GPS clock.
http://www.timetoolsglobal.com/