On Mon, 17 Jul 2006, Mark Rages wrote:

> On 7/16/06, Kevin <kben@dca.net> wrote:
> > I have a pic16f88, I am using the 10 bit ADC to read an
> > LM34DZ. The LM34DZ puts out 10mV per degree F from 0 F to
> > 100 F. I have the F88 ADC set to use VSS-VDD for reference,
> > 0 to 5V.
> > A couple weeks ago I was asking about a digital filter
> > to improve the accuracy of the ADC reading. Can anybody
> > provide me one or point to a web page that explains one.
> > This is strictly a hobby type project, and the LM34DZ will
> > be used in my house, so no extreme temps will be monitored.
> > If someone could provide an example with numbers plugged in
> > I would appreciate it.
> >
> > Thanks,
> > Kevin
> >
>
> You've received two good replies about filtering.  One (average five
> samples) is called an "FIR" filter and the other (moving average) is
> called an "IIR" filter.  Google these terms if you need more
> information.
>
> I would like to add that it's a good idea to use an analog filter
> before you sample the voltage.  It should be a lowpass filter that
> removes any noise above half the sampling frequency.  The digital
> filtering will work out better if you're not trying to filter aliased
> noise too.
>
> Regards,
> Mark
> markrages@gmail
>
Yes, now I have received three good answers !
All I want to do is read the LM34DZ with AN0, and a
HIH-4000, with AN5. I am using the F88 with the 8Mhz,
internal osc. The LM34DZ, puts out 10mV per degree F. The
HIH-4000 puts out a voltage between 1V and 4V, which you can
use to compute the realtaive humidity. I then take the ADC
readings and send them out the serial port to a PC at 19200.
Cuurently the ANO and AN5 are both hooked directly to their
respective devices.(LM34DZ and HIH-4000).
I have googled read the wikipedia on Digital Filters and
some other DSP pages, as well as Olin's respose a week or so
ago.
I was kind of looking for a real world example. What should
my sampling rate be ?  I only need to xmit a new temp and RH
every minute or so. I may add a Pressure sensor later. But,
besides sending the new reading to a PC the pic does nothing
else.
What sampling rate would you use ? This is where I was
hoping some one could tell me what they have used
effectively in the past.

Thanks again,
Kevin


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