Please I am having issue differentiating an analog signal.The signal output from the time domain math function(dx/dt) fluctuates indiscriminately.My sampling rate is 10k and samples to read is 10k.Please i need help in resolving this issue.Thanks.
Would have been best if you had saved the vi with data in the graph ;), but I think I know what problems you have.
Take a look at the Savitzky-Golay filter, that filter actually does a fit and can do a differentiantion more robust to noise. (Use the advanced FIR SG coeff vi and the help .... more theorie here)
Some of your problems might also come from filterartifacs, so capture some more data and cut the ends to avoid that.