Does the USB-4065 have memory to store a number of measurements taken by external trigger to be retrieved later? If so, how many measurements can be stored? Also, do the NI meters support driverless usage via something like SCPI?
The USB-4065 does have an onboard buffer, but it is only used to account for delays in transferring data to a computer over the USB bus. There's no provision for storing measurements in the onboard buffer for longer than is needed to transfer the data off the device. There is an option to take multiple measurements from an external trigger, and only read them back once complete, but in this mode the measurements are stored in a memory buffer on the host PC.
The USB-4065 requires the NI-DMM driver to function. The NI-DMM driver is IVI compliant if your concern is keeping your test code device independent. However, the USB-4065 is not SCPI compliant.
It sounds like you're exploring options for a project, and it's hard to give advice without fully understanding your needs. If you'd like to give us a call at (866) 275-6964, we can open a service request and discus your requirements further.
Michael B. Technical Support Engineer National Instruments