Calculator Inputs
Example Data Table
| Sensor | Method | R0 | Measured Resistance | Typical Temperature |
|---|---|---|---|---|
| Pt100 RTD | Callendar Van Dusen | 100 Ω at 0°C | 138.5055 Ω | About 100°C |
| Pt1000 RTD | Callendar Van Dusen | 1000 Ω at 0°C | 1097.35 Ω | About 25°C |
| 10k NTC | Beta Model | 10000 Ω at 25°C | 10000 Ω | About 25°C |
| Linear Copper Sensor | Linear Coefficient | 100 Ω at 20°C | 115 Ω | Depends on alpha |
Formula Used
Linear Coefficient Method
T = T0 + (R - R0) / (α × R0)
This method uses a reference resistance, reference temperature, and temperature coefficient.
NTC Thermistor Beta Method
1 / T = 1 / T0 + ln(R / R0) / β
Temperatures in this equation use Kelvin. The final result is converted into Celsius and Fahrenheit.
RTD Callendar Van Dusen Method
R = R0(1 + AT + BT²) for temperatures at or above 0°C.
Below 0°C, the calculator adds the C(T - 100)T³ term and solves iteratively.
How to Use This Calculator
- Measure the sensor resistance with a reliable meter.
- Select the correct sensor method from the menu.
- Enter R0, reference temperature, and model constants.
- Add lead resistance when the wiring creates measurement bias.
- Enter meter uncertainty and tolerance for error review.
- Press the calculate button to view the temperature result.
- Download the CSV or PDF report for your records.
Resistance to Temperature Conversion Guide
Why Resistance Conversion Matters
Resistance temperature conversion connects an electrical reading to a physical heat value. It is useful when a probe reports ohms instead of degrees. The calculator supports common field cases. You can model platinum RTDs, NTC thermistors, and simple linear sensors.
RTD Sensor Behavior
An RTD changes resistance almost linearly near room temperature. Platinum devices often use 100 ohms or 1000 ohms at zero degrees Celsius. For better accuracy, the Callendar Van Dusen equation is used. It handles wider ranges than a plain coefficient formula. The tool also subtracts estimated lead resistance. That matters in two wire and three wire installations.
Thermistor Behavior
Thermistors behave differently. Their resistance drops as temperature rises. The beta model is a practical engineering method. It uses reference resistance, reference temperature, and a beta constant. It is not perfect across every range. Still, it gives fast results for many NTC probes.
Linear Sensor Checks
Linear coefficient conversion is helpful for simple materials. It uses a reference point and temperature coefficient. This method is easy to audit. It is also useful for rough checks when a full sensor curve is not available.
Uncertainty Review
The calculator also estimates uncertainty. It combines resistance meter uncertainty with sensor tolerance. Then it converts the resistance error into temperature error. This helps judge whether a reading is acceptable. A small resistance error can create a large temperature error on some thermistors.
Field Use
Use this tool during calibration, troubleshooting, panel testing, and maintenance checks. Enter measured resistance first. Then select the sensor model. Add the correct reference values from the datasheet. Choose the wiring style. Review the corrected resistance before trusting the final temperature.
Best Practice
Good inputs matter. Use stable leads. Let the probe settle. Avoid self heating from high measurement current. Compare the result with expected process conditions. Export the CSV for records. Save the report when you need a quick service note.
For best practice, keep the selected model tied to one real sensor part. Do not mix a generic beta value with another thermistor curve. Check the datasheet range before using high temperatures. RTD equations are strong, but wiring mistakes still cause bias. Thermistor equations are sensitive to beta accuracy. The exported values make repeat testing easier for teams. They also support traceable notes. That keeps maintenance records clear and useful.
FAQs
What does this calculator convert?
It converts measured resistance into temperature using RTD, thermistor, or linear coefficient formulas. It also shows corrected resistance and uncertainty estimates.
Which method should I choose for a Pt100 sensor?
Use the RTD Callendar Van Dusen method. Set R0 to 100 ohms unless your datasheet gives another value.
Which method should I choose for a 10k thermistor?
Use the NTC thermistor beta method. Enter 10000 ohms as R0 if the thermistor is rated 10k at the reference temperature.
Why is lead resistance important?
Lead wire adds resistance to the reading. This can make the calculated temperature too high or too low, depending on the sensor type.
What is sensor tolerance?
Sensor tolerance is the possible resistance error from the sensor itself. The calculator uses it to estimate temperature uncertainty.
Can I use custom RTD coefficients?
Yes. Enter A, B, and C values from your datasheet. The default values match common platinum RTD calculations.
Why is the thermistor result approximate?
The beta equation simplifies the thermistor curve. It is useful for quick checks, but lookup tables are better for critical work.
Can I export the result?
Yes. Use the CSV button for spreadsheet records. Use the PDF button for a simple printable service report.