Time stamping the start of a measurement, from IRIG-B. To sync data data from external systems

[Lazer723]

I've got an interesting configuration. In short I have two data acquisition systems, one is NI-PXIe chassis based, and the other is a highly custom, closed DAQ system, however, it does support synchronising its sample clock from an input IRIG-B signal.

I need to acquire data from both and have the data from them be synchronised. I know that I can feed both the custom system, and the PXIe system an IRIG-B signal from a timecode generator, using a timing card like the PXIe-6683. However, this will only synchronise their respective internal clocks. I dont really have a way of reliably triggering the acquisition of both systems at the exact same time.

The data from the custom system will timestamp the data according to the IRIG-B signal, but I am unsure how to get the PXIe system to do the same (acquiring through a PXIe-4499 DSA card). Otherwise I will end up with two datasets that are offset from eachother by an unknown number of samples.

Any ideas on reliably writing the start time at least, to the TDMS output file?

[ZYOng]

You can use niSync Create Future Time Event (VI) with PXI-6683 to send a digital pulse at a specific time as the start trigger to your DSA device.

[Lazer723]

I see. I could set it so LabView instructs the custom DAQ system to begin measuring and the PXI chassis to begin measuring at [current time+50ms]. Since the current time will be based on the IRIG-B signal, the data would be able to be matched up. The timestamps will be known as long as I save the [current time+50ms] timestamp to the tdms file.

I suppose I would need to let the PXIe chassis know to discipline its clock to the IRIG-B signal in a prior instruction.

[Lazer723]

Is there a way to save the timestamp at which the acquisition begins if it was triggered externally through an input trigger signal?