MrrM Posted March 25, 2014 Report Share Posted March 25, 2014 Hi,I've a PXI-7841R (FPGA).My VI needs to send the derivative of a sine wave (volts) to an external card and acquire a sine wave input (velocity) that I have to integrate. The sine wave later become with two harmonics.When the frequency is too high, I notice aliasing problems and the sine's derivative amplitude and integral are not exact. Checking with simulink, for example with a sinusoid of amplitude 1, the integral should have amplitude 2 and the derivative 1. I have attached a screenshot of simulink and VI simple to check if the integral and the derivative values are corrected, by changing the frequency. Any help would be appreciated. Regards dev int simulate - Copia.vi Quote Link to comment
chris754 Posted March 25, 2014 Report Share Posted March 25, 2014 Integral of b*sin(ax) = -(b/a)cos(ax)+cDerivative of b*sin(ax) = ab*sin(x) In you example a=1, b=1 and c=1. They all have an amplitude of 2, but your integral is shifted up 1. Quote Link to comment
0_o Posted March 25, 2014 Report Share Posted March 25, 2014 I didn't read the post yet the calculation caught my eye. chris754, I guess you wanted to write in the derivative = abCos(ax) Quote Link to comment
MrrM Posted March 25, 2014 Author Report Share Posted March 25, 2014 sorry "......Checking with simulink, for example with a sinusoid of amplitude 1, the integral should have amplitude 1 and the derivative 1...." The problem is in Labview when I change frequency the sine's derivative amplitude and integral are not exact. Quote Link to comment
chris754 Posted March 26, 2014 Report Share Posted March 26, 2014 I didn't read the post yet the calculation caught my eye.chris754, I guess you wanted to write in the derivative = abCos(ax) yes, sorry, I meant cos not sin, thank you. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.