Hello Liming,
The DMM is capable of sending TTL triggers out on both the PXI_Trig lines and on the AUX connector on the front connection. These signals are intended for controlling National Instruments switch modules and not powering/closing third party relays.
If you're looking to control a National Instruments Switch there are example programs that demonstrate synchronous scanning with DMMs and Switches. To locate these examples open LabVIEW and go to Help» Find Exampled... Then Navigate to Hardware Input and Output» Modular Instruments» NI-Switch (Switches).
If this isn't what you're looking to do, or if you have additional questions, please feel free to post back with more information.
Have a great weekend!
Brooks
