loop timing to use time in differentiation vi

[NIUGOON]

attched is my vi, i need to have my data graphing as a function of time (seconds) in order to do differentiation to get my velocity. I tried using sample clock and implicit timing as well as elapsed time vi but never got data as a function of time rather only as a function of sample number. Please help!

[NIUGOON]

i basically just want to get the velocity of the linear potentiometer. I get readings and a graph for the voltage of a function of sample number, but i cant get the differentiator to work

[crossrulz]

Why not just setup DAQmx to continuously sample the DAQ channel.  Then you just read all of the available samples.  You can easily perform your derivative measurements from that array and you know exactly what the dt is since it will be hardware timed instead of software timed.