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50
100
150
200
250
300
350
−200 0 200 400 600 800
Temperature (°C)
Resistance ()
RTD Response
Corrected Response
Linearization Correction
G000
−1
0
1
2
3
4
5
−200 0 200 400 600 800
Temperature (°C)
Nonlinearity (%)
Uncorrected
Corrected
G000
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Appendix
8.1.4 Linearity Correction
Figure 41 illustrates how the XTR108 linearity correction works. The RTD has a response that is
approximately quadratic (gray line). The positive feedback of the input signal through the linearity DAC I
LIN
generates a response that is also approximately quadratic (black line). The two responses counteract
each other to generate a linear output (red line).
Figure 41. Linearity Correction Method
Figure 42 shows the uncorrected and corrected nonlinearity for a typical RTD. Normally a 40:1
improvement is achieved using this method.
Figure 42. Linearity Improvement
55
SBOU123March 2012 XTR108EVM-USB Evaluation Board and Software Tutorial
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