Re: [odin-devel] sinusoidal gradients

[Thies J. <th...@jo...>]

Dear Lazar,

can you please post the relevant part of your code?

Thank you, Thies


On Freitag, 3. April 2009, Lazar Fleysher wrote:
> Hello everybody,
>
> I can not seem to be able to make sinusoidal-shaped gradients.
> I was thinking about using trapesoidal gradients and set the rapmtype
> to "half_sinusoidal".
> Then I made a calculation for the integral, max gradient and
> rampduration so that the
> shape of the gradient will be a sinus (with horizontal part of the
> trapezoid equal to zero, only ramps).
> Instead, I seem to observe that some horizontal part of the gradient
> is kept and the gradient amplitude
> is reduced to produce correct gradient intergral. I know that if I set
> the total length of the gradient to
> a very short one, I will exceed the allowed gradient slewrate and this
> would happen. But I have done
> checking and the slewrate is 1/3 of the maximum. This indicates that
> there is some sort of hard limit
> on the minimum duration of the horizontal part of the gradient which
> is substantial. I could not find where
> it was set in the code.
>
> Am I trying to do something illegal? maybe it is a design feature
> based on some limits which I do not understand,
> but then, how to make sinusoidal gradients?
>
> Thanks a lot for your help
>
> Lazar
>
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