Convert Acquired Resistance From RTD Sensors Into Temperature Value

Updated Apr 7, 2025

Environment

Software

  • LabVIEW

I have an RTD sensor and I am acquiring resistance value and want to use LabVIEW to convert acquired resistance values to temperature values in Celsius degrees.

LabVIEW provides different functions to convert resistance into temperature, however, sometimes there is a need to do it manually using the corresponding formula. In this example, the PT1000 RTD sensor will be used.

We use the Callendar-Van Dusen equation:

R(T) = R0(1 + A×T + B×T2 – 100×C×T3 + C×T4) 

Where:

  • R(T) = RTD resistance at temperature T (°C), replace with your acquired RTD resistance value
  • R0 = RTD resistance at 0°C, R0 = 1000 Resistance at 0°C for PT1000 RTD
  • A, B, and C constants are derived from experimentally determined parameters and regulated by the IEC751 standard. You can check the datasheet of the sensors because usually, the coefficients are provided by RTD manufacturers.  
  • For Pt100 and PT1000 RTD sensors, the constants are the following:
    • A = 3.90830 × 10^(- 3)
    • B = -5.77500 × 10^(- 7)
    • C= 4.18301 × 10^(- 12) for -200°C ≤ T ≤ 0°C
    • C= 0 for 0°C for ≤ T ≤ 850°C. 
  • Temperature (T) can be calculated by solving the quadratic equation if we ignore the coefficient C = 4.18301 × 10 - 12 for negative temperature:
    • T = (-A + sqrt(A^2 - 4B×(1 - RT/R0))) / (2×B);

 

This is the logic implemented in the example code:

Download the attached example, set corresponding A and B constants for your sensor, insert R0 and use Resistance control to convert acquired resistance value and observe the result on a Temperature Indicator.

The attached example can be used as a subVI in LabVIEW code.