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Thermocouple vs. Thermopile: Key Differences Explained

thermocouple thermopile sensor temperature measurement infrared

This article compares thermocouple and thermopile sensors, highlighting the key differences between them.

What is a Thermocouple?

A thermocouple is an electrical device constructed from two dissimilar conductors that form electrical junctions at different temperatures.

Thermocouple structure and mathematical equation

It generates a voltage that depends on the temperature difference between these junctions. This phenomenon, known as the thermoelectric effect, makes thermocouples thermoelectric transducers.

What is a Thermopile?

A thermopile consists of multiple thermocouples arranged in series or parallel.

Thermopile structure and mathematical equation

It produces a higher voltage output than a single thermocouple. Unlike thermocouples, which are contact-based temperature sensors, thermopiles are non-contact temperature sensors. They use infrared radiation for temperature measurement, typically incorporating an IR absorber device.

Thermocouple vs. Thermopile: Key Differences

The following table summarizes the comparison between thermocouples and thermopile sensors:

Features	Thermocouple	Thermopile
Size	Thinner and has a pointed end	Bigger and thicker
Voltage output	Lower, typically between 8 mV to 30 mV	Higher, in the range of 10s or 100s of mVs
Structure	Two dissimilar conductors (single pair of wires)	More than one thermocouple arranged in series/parallel along with an IR absorber membrane
Mathematical Equation	$V_{out} = S \cdot (T_x - T_{REF})$	$V_{out} = N \cdot S \cdot (T_x - T_{REF})$ where $N$ is the number of thermocouples used in a thermopile
Application	Contact-based temperature measurement	Non-contact-based temperature measurement using IR (infrared radiation)