Synchronizing PXIe-408x DMMs Within a Chassis

Issue Details

Based on the Synchronizing Two DMMs with and External Trigger example, it seems like I cannot share a clock between two PXI-407x DMM devices. Is this the same for the PXIe-408x series?

Solution

Unlike the PXI-407x line, the PXIe-408x series of Digital Multimeters works off of the PXIe-Clk100 timebase from your PXI chassis to derive their sample clocks. This means that if you need to synchronize two PXIe-408x series DMMs in the same chassis, you will need to do the following: 

• Set the same sample rate for both devices. As they will have the same timebase, they will use the same timebase to derive their sample clocks.
• Send the same trigger to both devices.

Additional Information

This level of synchronization should be able to maintain a consistent synchronization over a period of time (i.e., the two sample clocks should not become further and further misaligned as time goes on). There will likely still be a small amount of cycle-to-cycle jitter present between the two measurements, causing a corresponding non-zero relative jitter between the devices' sample clocks. 

You cannot share clocks between PXI-407x devices in a chassis; the best synchronization you can achieve between multiple PXI-407x devices is sharing a start trigger. Generally, this is more than sufficient, as the trigger will tell the DMM when to acquire their finite set of samples. 

For more information on synchronizing please refer to Synchronization Explained.