NI 9421 continues sampling

[leq12]

I have 4 pulse output flow meters (https://www.omega.com/pptst/FTB4600.html)

all the flow meters connected to NI 9421 and cDAQ 9185 chassis to get my frequency readings using the DAQ assistant. i realized that for continues sampling,  i couldn't change my sample rate which is fixed as 1kHz ,without changing the timing type from implicit to sample clock. However. i have many option and anything i choose results in an error. any ideas on how i can fix this? 

i have attached a vi that i was testing for 1 flow meter.

[Conner.A]

A few questions:

1. What error are you getting when you run your code?

2. What sample clock settings are you using?

My initial impression is that your clock source isn't set properly. Try using ai/SampleClock and let us know how that goes.