RTD to Temperature Calculator

Precise RTD Conversions: Effortless Resistance to Temperature

 

Do you work with RTD temperature sensors and need a quick and reliable way to convert their values? Interpreting resistance readings from a PT100, PT1000, or other RTD can be a tedious and error-prone process if done manually using tables or the complex Callendar-Van Dusen formulas.

 

Our RTD Calculator is designed to eliminate this complexity, providing an instant and accurate solution for professionals and enthusiasts.

 

How does this tool help you?

 

• Versatile Bidirectional Calculation: Unlike basic tools, our calculator lets you work in both directions. You can convert a measured resistance in Ohms (Ω) to its equivalent temperature (°C, °F, K) and, with just one click, reverse the calculation to find out what theoretical resistance your sensor should have at a specific temperature.

• Support for Common RTDs: Easily select from the most commonly used RTD types in the industry, such as PT100 and PT1000. The tool preloads standard coefficients to streamline your work.

• Precision and Flexibility: For applications requiring maximum accuracy or the use of non-standard sensors, you can manually enter the Alpha (α) coefficient of your specific RTD (thermometer type), ensuring that the results are perfectly matched to your equipment.

• Immediate and Clear Results: Forget spreadsheets and formula searches. Get the conversion you need instantly, with your choice of decimal places and temperature unit.

 

This calculator is an indispensable tool for process engineers, maintenance technicians, instrumentation students, and any electronics enthusiast who needs accurate and reliable temperature measurements. Use it to streamline your workflow and ensure the accuracy of your data.

 

How to Use:

 

1. Select RTD Type: Choose the type of sensor you are using (PT100, PT1000 or other).

2. Enter the Values: Depending on the calculation mode selected, enter the resistance in ohms or the temperature in the desired unit.

3. Configure the Parameters: Adjust the alpha coefficient and temperature unit as needed.

4. Click on Calculate: Get the result instantly in the desired unit.

5. Reverse Calculation: Switches between calculating resistance from temperature or temperature from resistance.

 

This calculator is essential for applications requiring high-precision temperature measurement using RTD sensors. Try it now and simplify your technical calculations!

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Callendar–Van Dusen equation (IEC 60751)

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The resistance of a platinum RTD (Pt100, Pt500, Pt1000) versus temperature follows the Callendar–Van Dusen equation, where R₀ is the resistance at 0 °C (100 Ω for a Pt100):

For T ≥ 0 °C: R(T) = R₀ · (1 + A·T + B·T²)

For T < 0 °C: R(T) = R₀ · (1 + A·T + B·T² + C·(T − 100)·T³)

A = 3.9083 × 10⁻³ B = −5.775 × 10⁻⁷ C = −4.183 × 10⁻¹² (α = 0.00385)

To get temperature from resistance (T ≥ 0 °C), solve the quadratic equation:

T = [ −A + √(A² − 4·B·(1 − R/R₀)) ] / (2·B)

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Worked example

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A Pt100 reads 110 Ω. 1 − R/R₀ = −0.1; A² − 4·B·(−0.1) = 1.5044 × 10⁻⁵ and its square root is 0.0038786. T = (−0.0039083 + 0.0038786) / (−1.155 × 10⁻⁶) ≈ 25.68 °C.

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Pt100 and Pt1000 resistance table (α = 0.00385)

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Temperature · Pt100 resistance (Ω). For a Pt1000 multiply by 10. If your transmitter outputs a current loop, convert it with the 4-20 mA calculator; between table values use linear interpolation.

−50 °C (−58 °F) = 80.31 Ω

−40 °C (−40 °F) = 84.27 Ω

−30 °C (−22 °F) = 88.22 Ω

−20 °C (−4 °F) = 92.16 Ω

−10 °C (14 °F) = 96.09 Ω

0 °C (32 °F) = 100.00 Ω

10 °C (50 °F) = 103.90 Ω

20 °C (68 °F) = 107.79 Ω

30 °C (86 °F) = 111.67 Ω

40 °C (104 °F) = 115.54 Ω

50 °C (122 °F) = 119.40 Ω

60 °C (140 °F) = 123.24 Ω

70 °C (158 °F) = 127.08 Ω

80 °C (176 °F) = 130.90 Ω

90 °C (194 °F) = 134.71 Ω

100 °C (212 °F) = 138.51 Ω

110 °C (230 °F) = 142.29 Ω

120 °C (248 °F) = 146.07 Ω

130 °C (266 °F) = 149.83 Ω

140 °C (284 °F) = 153.58 Ω

150 °C (302 °F) = 157.33 Ω

160 °C (320 °F) = 161.05 Ω

170 °C (338 °F) = 164.77 Ω

180 °C (356 °F) = 168.48 Ω

190 °C (374 °F) = 172.17 Ω

200 °C (392 °F) = 175.86 Ω

210 °C (410 °F) = 179.53 Ω

220 °C (428 °F) = 183.19 Ω

230 °C (446 °F) = 186.84 Ω

240 °C (464 °F) = 190.47 Ω

250 °C (482 °F) = 194.10 Ω

260 °C (500 °F) = 197.71 Ω

270 °C (518 °F) = 201.31 Ω

280 °C (536 °F) = 204.90 Ω

290 °C (554 °F) = 208.48 Ω

300 °C (572 °F) = 212.05 Ω

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IEC 60751 tolerance classes

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Class AA: ±(0.10 + 0.0017·|t|) °C, i.e. ±0.27 °C at 100 °C.

Class A: ±(0.15 + 0.002·|t|) °C, i.e. ±0.35 °C at 100 °C.

Class B: ±(0.30 + 0.005·|t|) °C, i.e. ±0.80 °C at 100 °C.

Class C: ±(0.60 + 0.010·|t|) °C, i.e. ±1.60 °C at 100 °C.

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Frequently asked questions

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What is the difference between α = 0.00385 and 0.00392?

0.00385 is the industrial standard (IEC 60751 / ASTM E1137); 0.00392 is purer platinum used in some older US sensors. Using the wrong alpha causes errors of up to 1 °C at 50 °C.

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Pt100 or Pt1000?

A Pt1000 gives 10 times more signal, so lead-wire resistance matters 10 times less, which makes it better for 2-wire connections. Pt100 is more common in industry with 3- or 4-wire connections.

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Why use 3 or 4 wires?

Every ohm of lead resistance on a 2-wire Pt100 adds about 2.6 °C of error. A 3-wire connection compensates the leads; a 4-wire connection removes them completely.