- From: Tuomas Räsänen <tuomas.rasanen_at_ssf.fi>
- Date: Wed, 16 Mar 2005 18:50:12 +0200
Hello,
I think you need to check the hardware first.
If you have an oscilloscope, find out what makes the noise (I guess 50 Hz might
be the biggest culprit).
If you find a lot of noise in the raw measurement signal, next thing is to see
whether your equipment is grounded and shielded properly (Web will have a lot of
info about this topic).
If the noise level remains to be too high (p-p is more than your minimum
tolerable error), you'll do analog low-pass filtering. See that the output is
cut very low at half of your sampling rate, so that you don't get any
significant aliasing.
As you measure temperature, I guess you have a slowly varying signal. You could
just put a simple RC-filter:
_____
---| R |--o----O A/D -converter F(3 dB) = 1/(2*pi*R*C),
----- | drop is about 6 dB per octave.
=== C
|
Gnd
with 3 dB cutoff at say 0.5 Hz and sampling rate say 10 Hz. Then you could
digitally low-pass filter the signal to be able to get the final data at a lower
rate.
Active filters are of course more efficient.
If there is a danger of sudden transient-like spikes, it's helpful to do a
3-point median filtering.
Eric Hudson wrote:
> Hello all,
>
> I have included a link below to my code with output that accepts constant 10mV
> input. The problem I am having as you shall see from the output is bad values.
> What can I do to fix this problem? I'm trying to make my program as accurate
> as possible.
>
> http://www.rafb.net/paste/results/S1qqEN74.html
>
>
> Thanks,
>
> Eric
>
> _______________________________________________
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Regards,
-- Tuomas
--------------------------------------------------------------
Tuomas Räsänen tuomas.rasanen_at_ssf.fi
Space Systems Finland +358 9 613 28654
Kappelitie 6, 02200 Espoo mobile: 050 330 1758
Received on 2005-03-16Z16:50:12