Re: method for digital filtering

teilersen wrote:
Hi

I am working on a project where I need to filter some measurements from a
belt-scale. My problem is that the scale will perform a damped vibration
when an object is applied which will corrupt my signal. The signal will
also be corrupted with sinusoids from e.g. unbalanced drive units. The
actual signal I measure consists of a lot of damped sinusoids.
The scale can be modeled as a metal plate mounted on stiff springs and the
desired output is close to a step-function with the amplitude equal to the
weigth of the object. The accuracy needs to be very high and the filter
needs to be as fast as possible. I do not expect to be able to use a lowpass FIR or IIR as the stepfunction
contains all frequencies in the freq-domain.

What do you mean: you can't low-pass filter because the step function's components go out to infinity? In the first place, they don't. You should see a ramp as the weight is smoothly transfered to the scale, then off again. Surely, there is no impact! Moreover, you *must* low-pass filter to remove all components at and above half the sampling frequency *before* the analog signal is digitized. You need to discuss more of your problem and how to solve it.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
.

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