Two 6143 sychronized to external pulse

[lpaal]

We have two 6143s in one PC with Labview.  Need to synchronize the sampling with an external pulse train.  We need 100 samples/sec, have 10 MHz ref and 1000, 100, 10, and 1 PPS external TTl signal available.  Idially the samples should be timetagged accurately (the PC clock drifts too much).  Both cards should take sample at the same time. 

New to the cards and Labview, got the sample taking, timetag working under the PC clock, found not accurate enough.

Thanks for any help.

Leslie.

[dansch]

Hello Leslie,

I assume these PPS signals are coming from some kind of GPS receiver. You can synchronize your devices by using this external signal as your sample clock, and then share the sample clock between the boards. An example of this can be found within the LabVIEW examples under DAQmx >> Synchronization >> Multi-Device >> Multi-Device Synch-Shared Ext Sample Clk.vi. You can configure your master device to use the external signal as its sample clock, and then configure the slave device to use the sample clock of the master. To properly synchronize the boards, you will need to connect them within the PC using a RTSI cable. For more information about the RTSI bus, please refer to Chapter 11 of the S Series User Manual.

In regards to timestamping the data, the initial time returned for the acquisition will be based on the system time. This time may not necessarily be exactly the same as the absolute time of the GPS receiver, but using the PPS signal as your timing source will ensure that the samples are all taken at exact intervals in time with respect to the GPS. Hope this helps,