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<div class="moz-cite-prefix">On 01/27/2014 11:47 PM, Scott Hall
wrote:<br>
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<div class="moz-cite-prefix">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.<br>
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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 <a
href="http://www.atmel.com/images/doc8108.pdf">app note</a> that
makes it clear that the sensor isn't at all linear and to get to +/-
2C takes a pair of calibration points for <b>each</b> 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. <br>
<br>
-Pete<br>
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On 01/27/2014 04:18 PM, Pete Soper wrote:<br>
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<blockquote cite="mid:52E6CD2D.8030403@soper.us" type="cite">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? <br>
<br>
-Pete <br>
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<pre class="moz-signature" cols="80">--
Scott G. Hall
Raleigh, NC, USA
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:ScottGHall1@GMail.Com">ScottGHall1@GMail.Com</a>
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