The accuracy of the measured temperature is related to the accuracy of all elements. For example, a 4.7kΩ
resistor is set as the pull-up resistor but the measured value using a precise LCR meter is 4635 Ω.
The image below shows the resistance vs. temperature curve for a PT1000 sensor.
Temperature = -243 + 0.236x + 5.93E-06x² + 1.16E-09x³
a = -243, a = 0.236, a = 5.93E-06
If a higher sensitivity in a particular range of temperatures is required, the polynomial can be calculated only
for that range of temperatures.
Note
For defining the protection level, one point is enough and the polynomial function is not required.
For example, the resistance value can be calculated for 90° in Node:
The resistance of a PT1000 is 1353 for 90° C, the input resistance of Node is 20.4 kΩ, and the resistance value
0
1
2
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