RTD Resistance to Temperature Calculator for Water

RTD Resistance Equation:

\[ R = R_0 [1 + A t + B t^2 + C (t - 100) t^3] \]

Reference Resistance (R₀):

Coefficient A:

Coefficient B:

Coefficient C:

Temperature (t):

°C

Calculated Resistance (R):

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1. What is the RTD Resistance Equation?

The RTD (Resistance Temperature Detector) resistance equation calculates the resistance of a platinum RTD at a given temperature in water. The equation accounts for the non-linear relationship between resistance and temperature.

2. How Does the Calculator Work?

The calculator uses the RTD resistance equation:

\[ R = R_0 [1 + A t + B t^2 + C (t - 100) t^3] \]

Where:

\( R \) — Resistance at temperature t (Ω)
\( R_0 \) — Reference resistance at 0°C (Ω)
\( A \) — Linear temperature coefficient (typically 3.9083×10⁻³ °C⁻¹)
\( B \) — Quadratic temperature coefficient (typically -5.775×10⁻⁷ °C⁻²)
\( C \) — Cubic temperature coefficient (for t < 0°C, typically -4.183×10⁻¹² °C⁻⁴)
\( t \) — Temperature (°C)

Explanation: The equation models the resistance-temperature relationship of platinum RTDs, with different terms accounting for linear and non-linear behavior.

3. Importance of RTD Resistance Calculation

Details: Accurate resistance calculation is crucial for temperature measurement systems using RTDs, calibration procedures, and sensor design.

4. Using the Calculator

Tips: Enter reference resistance (R₀) in ohms, temperature coefficients (A, B, C), and temperature in °C. Default values are provided for standard platinum RTD (PT100).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical R₀ value for platinum RTDs?
A: Common values are 100Ω (PT100) and 1000Ω (PT1000) at 0°C.

Q2: Why are there different coefficients for different temperature ranges?
A: The resistance-temperature relationship of platinum is not perfectly linear, requiring higher-order terms for accuracy.

Q3: How accurate is this calculation?
A: For standard platinum RTDs, the equation provides accuracy within ±0.1°C in the range -200°C to +850°C.

Q4: What's the difference between this and the Callendar-Van Dusen equation?
A: This is a form of the Callendar-Van Dusen equation simplified for temperatures above 0°C in water.

Q5: Can I use this for other liquids besides water?
A: The coefficients may need adjustment for different media as heat transfer characteristics vary.