Formula & Calculator
Thermocouple Seebeck Voltage
The voltage generated by a thermocouple junction is proportional to the temperature difference across it.
Interpretation
Thermocouple Seebeck voltage V = S·ΔT is the voltage generated across two dissimilar metals due to a temperature difference.
The Seebeck coefficient S is material‑dependent.
Example: S=40µV/°C, ΔT=100°C → V = 40e-6 × 100 = 4 mV.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| V | Seebeck voltage (thermocouple output) | µV |
| S | Seebeck coefficient (thermopower) | µV/°C |
| ΔT | Temperature difference (hot junction – cold junction) | °C |
What it means
The Seebeck effect generates a voltage V between two junctions of dissimilar metals when there is a temperature difference ΔT between them. The voltage is given by V = S·ΔT, where S is the Seebeck coefficient (material‑dependent). Thermocouples are widely used as temperature sensors because they are rugged, low‑cost, and have a wide range. The output voltage is small (typically µV/°C) and must be amplified. The relationship is approximately linear, but corrections are needed for high accuracy. Example: A type‑K thermocouple has a Seebeck coefficient of about 40 µV/°C. For a 100°C temperature difference, V = 40e-6 * 100 = 4 mV. This signal is measured to determine the temperature.
Worked example
Thermocouple Seebeck Voltage – Practical Example
Real‑World| Parameter | Value |
|---|---|
| S | 41 µV/°C |
| ΔT | 100 °C |
| Formula | V = S·ΔT |
Common mistakes
Watch unit consistency and the assumptions behind the formula; misapplying it outside its valid conditions is the most frequent error.Applications
Thermocouple Seebeck voltage V = S·ΔT generates a voltage proportional to the temperature difference between two junctions. This is the basis of thermocouple temperature measurement. Engineers use thermocouples in industrial process control, HVAC, and automotive applications. The Seebeck coefficient S determines sensitivity. Understanding this formula is essential for selecting and calibrating thermocouples.
- Temperature measurement in industrial and laboratory settings
- Process control and monitoring
- Automotive exhaust and engine temperature sensing
- HVAC temperature regulation
- Educational understanding of thermoelectric effects
Frequently Asked Questions
The Seebeck voltage is V = S·ΔT, where S is the Seebeck coefficient (thermopower) and ΔT is the temperature difference between the two junctions. It is the principle behind thermocouple temperature measurement.
Type K (chromel‑alumel): ~41 µV/°C; Type T (copper‑constantan): ~43 µV/°C; Type J (iron‑constantan): ~52 µV/°C.
The Seebeck coefficient is a function of temperature, so the voltage‑temperature relationship is non‑linear. Polynomial approximations are used.
Common errors: 1) using the wrong Seebeck coefficient, 2) forgetting the reference junction compensation, 3) using the voltage from a single junction (the thermocouple measures difference), 4) applying to non‑thermocouple materials, 5) not considering cold junction temperature.
Temperature measurement in industrial processes, engines, and household appliances.
Seebeck effect: temperature difference creates voltage. Peltier effect: current flow creates a temperature difference (thermoelectric cooling).
Measure the Seebeck voltage and use a reference junction at a known temperature (e.g., ice point). Modern instruments use electronic compensation.
Sensitivity is the Seebeck coefficient (µV/°C). Higher sensitivity gives a larger voltage per degree.