If you have multiple devices that support the IEEE 802.1AS standard, you can use Start Trigger synchronization to trigger at a specific time. These devices must either be connected through a daisy chain or a switch that supports IEEE 802.1AS.
For a detailed tutorial on synchronizing FieldDAQ devices, refer to Synchronizing Analog Input FieldDAQ Devices with NI-DAQmx in LabVIEW on ni.com.