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Date:	Fri, 6 Mar 2015 16:11:15 +0100
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Subject:	Re: [geda-user] [OT] Temperature sensor and control recommendation
From:	Bernhard Kraft <bkraf0j9 AT gmail DOT com>
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There are some free code examples around for implementing the "running
average" algorithm which is probably what you want. But I still think
you need a decent enough ADC (14-16 bit) to solve the requirements
(resolution = 450/0.3)

On Fri, Mar 6, 2015 at 11:58 AM, gene glick <geneglick AT optonline DOT net> wrote:
> On 03/05/2015 11:21 AM, DJ Delorie wrote:
>>
>>
>>> I'm facing the need to control the temperature of a small sample in a
>>> chamber between room temperature and about 450°C with a precision of
>>> 0.3°C or better.
>>
>>
>> I use a thermocouple to monitor my woodstove, but I don't care so much
>> about precision.  I use a DS2760 thermocouple kit from Parallax for
>> it, and a high-temp thermocouple probe from Omega.com.
>>
>> For monitoring my geothermal system, I used RTDs and an MCU's ADC to
>> measure them.  I got extra precision by doing each measurement 64
>> times and averaging, and the tech who calibrated my geothermal system
>> says they're spot-on.
>>
>> I use the same averaging trick on my thermostats to get 0.1F readings
>> on a 1C-rated sensor.  If your sensor isn't noisy enough to use this
>> trick, you can always add noise - you're basically building a 1-bit
>> ADC.
>>
>>
> we use this trick at work as well - converts a 12-bit ADC to 16-bit
> precision. I think the relationship requires you need 2^n samples for each
> bit of additional resolution. This is off the top of my head, but is
> probably close. So if I remember correctly, we had to sample an extra 16X to
> get the additional 4-bit precision. It works really well. But yes, it relies
> on noise to work and assumes the measurement is relatively stable over the
> sampling period.  I believe the technical term for this trick is decimation.
>
> gene
>
>

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