[TriEmbed] ATTiny84A internal temp sensor: how good?

[Pete Soper]

On 01/27/2014 11:47 PM, Scott Hall wrote:
> Are you trying to use it to measure atmospheric temperatures?  It was 
> designed to measure chip temperature, to help you program a shutdown 
> or minimizing sequence before the magic smoke comes out.  At work last 
> year we used it to activate a peizo cooling element as needed, but 
> minimized activation for longer battery life.  We always used an 
> external sensor for environmental conditions.
I'm trying to understand how calibration relates to the accuracy of this 
sensor and the 84A datasheet is worthless for that. Ron Craig pointed me 
to exactly the right Atmel app note 
<http://www.atmel.com/images/doc8108.pdf> that makes it clear that the 
sensor isn't at all linear and to get to +/- 2C takes a pair of 
calibration points for *each* span of 10-20 degrees across the range of 
interest. I would have guessed that support for temperature compensation 
is the aim of this kind of sensor in this kind of chip.

-Pete

>
> On 01/27/2014 04:18 PM, Pete Soper wrote:
>> The internal sensor in the ATTiny84A stinks without calibration. What 
>> I can't find in the datasheet (section 16.2) is how good it can get 
>> with additional calibration points. Would it be reasonable to expect 
>> to make it accurate to +/- two degrees C across a 0 to 70 degree 
>> range if I can calibrate it across the full range and refine the 
>> slope measurement or is the linearity likely to be too poor?
>>
>> -Pete
>>
>
>
> -- 
> Scott G. Hall
> Raleigh, NC, USA
> ScottGHall1 at GMail.Com
>
>
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