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Date:	Fri, 06 Mar 2015 05:58:29 -0500
From:	gene glick <geneglick AT optonline DOT net>
Subject:	Re: [geda-user] [OT] Temperature sensor and control recommendation
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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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