Resistance to Temperature Calculator

Calculator Form

Calculation model

Measured resistance

Measured unit

Reference resistance

Reference unit

Reference temperature °C

Alpha coefficient

Thermistor beta value K

CVD coefficient A

CVD coefficient B

CVD coefficient C

Lead compensation ohms

Resistance uncertainty ± ohms

Output unit

Decimal places

Low review limit °C

High review limit °C

Formula Used

Corrected resistance

Rcorr = Rmeasured - Rlead

Linear resistance model

T = Tref + ((Rcorr / Rref) - 1) / alpha

NTC thermistor beta model

T = 1 / ((1 / Tref,K) + ln(Rcorr / Rref) / beta) - 273.15

Platinum RTD Callendar Van Dusen model

R / R0 = 1 + AT + BT² above zero degrees Celsius.

R / R0 = 1 + AT + BT² + C(T - 100)T³ below zero degrees Celsius.

The calculator solves this model by iteration when the CVD option is selected.

How to Use This Calculator

Enter the measured sensor resistance.
Select the resistance unit used by your meter.
Enter the reference resistance from the sensor data sheet.
Choose the model that matches your sensor type.
Enter alpha, beta, or CVD coefficients as needed.
Add lead compensation when wiring resistance is known.
Select your required output unit.
Press the calculate button and review the result above the form.
Download CSV or PDF for your records.

Example Data Table

Sensor	Reference	Measured resistance	Model	Approximate result
Pt100	100 ohms at 0°C	138.51 ohms	CVD	About 100°C
Pt1000	1000 ohms at 0°C	1096.25 ohms	Linear alpha	About 25°C
NTC 10K	10000 ohms at 25°C	32650 ohms	Beta 3950	Near 0°C

Understanding Resistance to Temperature Conversion

Resistance temperature conversion turns an electrical reading into a usable heat value. It is common with RTDs, thermistors, and process probes. The idea is simple. A sensor changes resistance as its body warms or cools. The calculator compares the measured resistance with a known reference point. Then it applies the selected model.

Why Reference Values Matter

Reference resistance is the anchor for the conversion. For a Pt100 sensor, the reference is often 100 ohms at zero degrees Celsius. For a Pt1000 sensor, it is often 1000 ohms. Thermistors use another reference temperature, such as 25 degrees Celsius. The model needs that point before it can estimate any other temperature.

Choosing The Right Model

The linear model is useful for quick engineering estimates. It uses one coefficient, usually called alpha. It is easy to check and works well over a limited span. The Callendar Van Dusen model is better for platinum RTDs. It uses A, B, and C coefficients. It can improve accuracy, especially when the resistance is near the sensor standard range. The beta model is designed for NTC thermistors. It uses the beta constant and a reference temperature in kelvin.

Lead And Field Effects

Field wiring can add resistance. This extra resistance may make the sensor appear hotter. The lead compensation field lets you subtract known wiring resistance before calculation. Always measure wiring carefully. Small ohm errors can become large temperature errors with sensitive sensors.

Practical Use

Use this tool when checking control panels, laboratory sensors, HVAC probes, or maintenance logs. Enter the measured resistance first. Select the model that matches your sensor data sheet. Keep units consistent. Review the corrected resistance and warning notes. Export the result for records when needed.

Accuracy Notes

No calculator replaces calibration. Sensor class, aging, self heating, moisture, and meter accuracy all affect the final value. Treat the output as an estimate unless your input data comes from calibrated equipment. For critical work, compare the result with a certified thermometer or a traceable calibration report.

Record the sensor type, meter range, and ambient conditions. These notes help future checks. They also make exported files more useful for audits, handovers, and repeat troubleshooting during planned maintenance or urgent repairs.

FAQs

What does this calculator convert?

It converts measured electrical resistance into an estimated temperature. The result depends on the selected sensor model, reference resistance, coefficients, and wiring correction.

Which model should I select?

Use the linear model for quick RTD estimates. Use CVD for platinum RTDs. Use the beta model for NTC thermistors with a known beta constant.

What is reference resistance?

Reference resistance is the sensor resistance at a known reference temperature. Pt100 usually means 100 ohms at 0°C. NTC thermistors often use 25°C.

What is lead compensation?

Lead compensation is known wiring resistance subtracted from the meter reading. It helps reduce temperature error caused by long or thin sensor wires.

Can I use this for Pt1000 sensors?

Yes. Enter 1000 as the reference resistance. Then choose a suitable linear alpha value or use the CVD model with correct coefficients.

Why does thermistor temperature fall when resistance rises?

Most NTC thermistors have negative temperature behavior. Their resistance rises when temperature falls, and resistance drops when temperature rises.

Is the output suitable for calibration certificates?

No. It is an engineering estimate. Use certified equipment, controlled conditions, and traceable standards for formal calibration documents.

Why do I see a review note?

Review notes appear when compensation is applied or when the result falls outside selected limits. They help you check unusual inputs before using the result.