9401 clock source for angle measurement

Hello 

I have a NI9401 on a C-DAQ9178 on slot 5. One encounter is connected to the 9401 and i created a task for the angular position measurement.

My problem is that I want to have continuous samples but I din't get the right clock source, so only 1 sample on demand works currently.

Does anyone have an idea how to configure the clock source?

Thank you very much in advance, 

Martin