1st order Filter with 2 second Time Constant

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digi001

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How do I design a 1st order filter with 2 second time constant?

1 / (s + ?)


Once i have it in continuous form I can convert using BiLinear and design the digital filter I need.
 

first order means an RC filter.....so RC product should be 2 seconds.
Put Z(r) = 1000 + j0
Put Z(c) = 0 + j. xc

where xc = 1/2.pi.f.C
Where C = 0.002 Farad

Now you can work it through and get vin/vout in complex numbers, ie the s parameter relation
 

I think i found now what I needed. Treez, i dont have any actual R's or C's so the problem is much simpler than that.

The form for 1st order Low Pass transfer function is:
1
----------
(1+s/wc)

with wc being the 'cutoff frequency' in radians per second

wc is the inverse of the time constant.

So actually it is very simple and my transfer function is just:
1
----------
(1+2s)


Converting to bilinear, i will let matlab handle it and give me coefficients

Thanks.
 

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