Which equation gives the most accurate RTD calculation?
A. Boyle’s Law
B. Ohm’s Law
C. Kirchhoff Law
D. Callendar-Van Dusen
View Answer
Correct Answer: D
Explanation:
While simple linear equations can provide approximate RTD temperature calculations, the Callendar-Van Dusen equation is the internationally accepted model for accurately describing the resistance-versus-temperature relationship of platinum RTDs such as Pt100 and Pt1000.
The Callendar-Van Dusen equation accounts for the non-linear behavior of RTDs over a wide temperature range and is used in industrial transmitters, temperature calibrators, and precision measurement systems.
For temperatures above 0°C:
Where:
- RT = Resistance at temperature T
- R₀ = Resistance at 0°C
- A and B = RTD constants defined by IEC 60751
- T = Temperature in °C
Why the other options are incorrect:
- Boyle’s Law → Relates pressure and volume of gases.
- Ohm’s Law → Relates voltage, current, and resistance in electrical circuits.
- Kirchhoff Law → Used for current and voltage analysis in electrical networks.
- Callendar-Van Dusen Equation → Specifically developed for accurate RTD temperature calculations.
Because RTD resistance changes non-linearly with temperature, the Callendar-Van Dusen equation provides the most accurate temperature calculation and is widely used in industrial instrumentation and calibration laboratories.