Precision Thermocouple Based Temperature Measurement System

Introduction

The objective of this project is to design, build, and validate a precision thermocouple-based temperature measurement system using the Seebeck effect. The system converts the extremely small thermoelectric voltage generated by a thermocouple into accurate, real-time temperature data. Unlike thermistors or integrated circuit temperature sensors, thermocouples are capable of:

• Operating over a very wide temperature range
• Withstanding harsh and high-temperature environments
• Responding rapidly due to low thermal mass

However, the output signal from a thermocouple lies in the microvolt range, making accurate measurement challenging. This project addresses that challenge by implementing:

• A low-noise instrumentation amplifier
• Cold junction compensation (CJC)
• Microcontroller-based digitization, linearization, and calibration

Theoretical Background

Seebeck Effect

The Seebeck effect states that when two dissimilar conductors are joined to form a loop and their junctions are maintained at different temperatures, a voltage is generated.

The thermoelectric voltage is given by: $V=S\cdot \mathrm{\Delta }T$ where:

• $V$ = thermoelectric voltage
• $S$ = Seebeck coefficient (µV/°C)
• $\mathrm{\Delta }T$ = temperature difference between junctions

For common thermocouples such as **Type K**: $S\approx 41\mu V{/}^{\circ }C$

Experimental Setup

Experimental Setup Of Thermocouple Measurement System

References

Oh, A. J., Stoddard, C. J., Queenan, C., & Oh, S. (2025). Efficient and affordable thermoelectric measurement setup using Arduino and LabVIEW for education and research. American Journal of Physics, 93(12), 991–999. https://doi.org/10.1119/5.0289649