Texas Instruments XTR108, User Manual

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−1
0
1
2
3
4
5
−200 0 200 400 600 800
Temperature (°C)
Nonlinearity (%)
Uncorrected
Corrected
G000
50
100
150
200
250
300
350
−200 0 200 400 600 800
Temperature (°C)
Resistance (
Ω
)
RTD Response
Corrected Response
Linearization Correction
G000
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Appendix
55 SBOU123A – March 2012 – Revised September 2016
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XTR108EVM-USB Evaluation Board and Software Tutorial
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