Calculator
Use the form below to convert measured thermocouple voltage into temperature with cold-junction compensation.
Example Data Table
These examples are generated by the same conversion logic used in the calculator.
| Type | Measured Voltage | Cold Junction | Corrected Voltage | Temperature | Temperature |
|---|---|---|---|---|---|
| K | 1.500 mV | 25.0 °C | 2.500242 mV | 61.558 °C | 142.804 °F |
| J | 2.800 mV | 20.0 °C | 3.819149 mV | 73.166 °C | 163.699 °F |
| T | 0.950 mV | 23.0 °C | 1.860781 mV | 45.888 °C | 114.598 °F |
| E | 4.500 mV | 25.0 °C | 5.995112 mV | 95.188 °C | 203.339 °F |
| N | 1.750 mV | 30.0 °C | 2.543015 mV | 92.149 °C | 197.868 °F |
Formula Used
This calculator uses thermocouple reference equations in two steps.
Step 1: Cold-junction compensation
Corrected EMF = Measured EMF + Reference EMF at junction temperature
Ecorrected = Emeasured + Eref(Tref)
Step 2: Voltage to temperature conversion
Temperature is found from the inverse piecewise polynomial for the selected type.
T = f^-1(Ecorrected)
For each thermocouple family, the page applies the correct coefficient range. Type K also includes its positive-temperature exponential adjustment term.
How to Use This Calculator
- Select the thermocouple type that matches your probe.
- Enter the measured thermocouple voltage in millivolts.
- Enter the reference junction temperature in degrees Celsius.
- Add an optional label for the reading or test point.
- Press the convert button to generate the result.
- Review corrected voltage, converted temperature, and sensitivity.
- Use the chart to inspect the local response curve.
- Download CSV or PDF for records, calibration notes, or reports.
Frequently Asked Questions
1) Why does this calculator ask for reference junction temperature?
Thermocouples measure temperature difference, not absolute temperature. The reference junction value lets the calculator add the proper compensation voltage before converting the corrected signal into final temperature.
2) What voltage unit should I enter?
Enter the measured thermocouple signal in millivolts. The script converts it internally into microvolts because the stored polynomial coefficients use microvolt-based reference relationships.
3) Which thermocouple types are supported here?
This version supports J, K, T, E, and N thermocouples. Those cover many bench, maintenance, and industrial measurement tasks while keeping the interface compact and practical.
4) Why can a negative voltage still produce a valid temperature?
A thermocouple can output negative EMF when the hot junction is below the reference condition. That behavior is normal and is handled by the negative-range polynomial for the selected type.
5) What does corrected voltage mean?
Corrected voltage is the measured signal after adding the reference junction EMF. It represents the equivalent thermocouple voltage relative to a 0°C reference junction.
6) Is the plotted line the full calibration curve?
The chart shows a local slice around the computed operating point. That makes nearby slope changes easier to inspect without compressing the graph across the full sensor range.
7) Can I use this for calibration paperwork?
Yes. The summary block, corrected voltage, and downloadable CSV or PDF outputs are suitable for lab notes, service logs, and quick engineering documentation.
8) Why might I see a range warning or no result?
That happens when the entered cold-junction temperature or corrected voltage falls outside the supported polynomial range for the selected thermocouple family.