Negative Temperature Coefficient Thermistors for Temperature ...
Negative Temperature Coefficient Thermistors for Temperature ...
Negative Temperature Coefficient Thermistors for Temperature ...
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8 <strong>Thermistors</strong><br />
Error° K<br />
0.1<br />
0.05<br />
-0.05<br />
Error plot <strong>for</strong> the squareless model<br />
260 280 300 320 340<br />
T ° K<br />
Figure 5<br />
As the figure shows, the error introduced into our example by dropping the squared term is typically less than 0.1°C . For many<br />
applications this would be acceptable.<br />
Even the simplified model requires taking a logarithm to find the temperature. For certain applications, such as those restricted<br />
to integer math on a microcontroller, this is undesirable. If the accuracy requirements aren’t too high, the logarithm can be<br />
avoided with a polynomial approximation.<br />
The true temperature vs voltage equation <strong>for</strong> our example can be found by combining (9) with (3) it is<br />
1<br />
1 s r 1 s Exp A <br />
v B<br />
<br />
T C D<br />
<br />
T2 T3 Setting (s)=1, and graphing<br />
(18)
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