NI Sync time drifting over time

[FatinNaz]

Hi all, im using labVIEW 2020 sp1 with 3 unit sbRIO 9609. These 3 sbRIO connected using an unmanaged network switch. Im trying to synchronize the timing for all sbRIO. Luckily it happen to sync but after some time, it drifted apart. Referring to attachment below, the graph drifted but the time for each sbRIO still sync, only the graph on HMI seems to drifted apart. Does anybody know why it drifted apart after some time and how to keep it sync?

[GerdW]

Hi Fatin,

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@FatinNaz wrote:

the graph drifted but the time for each sbRIO still sync, only the graph on HMI seems to drifted apart. Does anybody know why it drifted apart after some time and how to keep it sync?

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So you want us to analyze this problem by looking at some images of some frontpanels of your software?

What kind of answer do you expect when providing that type/amount of information?

[wiebe@CARYA]

Does the time sync actually change the CPU speed?

I think it does not, as these CPU's are clocked by a fixed crystal, not a VCO. So sampling with a fixed interval won't give you matching samples.

The time of the cRIOs will match, but a slower CPU will still have more samples per (real) hour than a faster one, as the CPU speed doesn't change and the sampling is regulated by the CPU speed, not the absolute time. The timestamp changes, but this is just a label.