UTC offset in PXI-6682

[poklad]

Hi!

I set NiSync time reference to GPS. I create Future Time Event and use this event as a start trigger for PXI-4462. But I have a delay on 35 sec, i.e. on UTC offset. How can I generate my event on UNC time? Only manualy add 35 sec to my UTC time? Or there is another way?

Jury

[AlejandroZepeda]

Hi.

The internal timebase of the PXI-6682 operates on TAI time, which is currently 35 seconds ahead of UTC (but this might change depending on future leap seconds).

Indeed, if you want to have your future time events to operate on UTC, you will have to manually add the TAI-UTC offset to the scheduled time.  Depending on how long you want your application to be valid, you can simply hard-wire that to a constant value of 35, or you can read the "UTC Offset" property.  However, there is a big caveat with this: the UTC offset information is only transmitted by the satellites every 12.5 minutes, so it can be up to 12.5 minutes after start-up before that property becomes valid.  There is another property, the "UTC Offset Valid" boolean, which you can use to determine if the former is already valid.

The discontinuities caused by leap seconds on UTC are hard to deal with, which is why the PXI-6682 uses the TAI timebase.

Hope this helps.

Regards,

Alejandro

[Travis-E]

Hello poklad,

Do you want to have a delay on your UTC time or is that the concern? Can you please post you code so I can gather more details on what you are doing? I will try setting up your hardware and seeing if I get the delay you encountered. 

Regards,

-Travis E