Last revised: December 11, 2024

Reviewed by: Scott Orlosky, consulting engineer

Temperature sensor chips are semiconductor dies or packages that have built-in temperature sensors. Temperature sensor chips are employed in measuring and controlling temperatures of various electric and electronic instruments. A temperature sensor chip infers temperature by featuring some changes in physical characteristic of electronic equipment. There are many different types of temperature sensors. Examples include thermocouples, resistance temperature devices (RTDs), infrared radiation sensors, bimetallic devices, liquid expansion devices, and change-of-state sensors. A temperature sensor chip protects equipment from high temperatures, which may damage the equipment. Thermoelectric thermometers, which use thermocouples are used in measuring temperatures. Resistance temperature detectors operate on the principle of changes in electrical resistance of pure metals. They are also characterized by a linear positive change in resistance with the temperature. Other temperature sensor chips are also commonly available.

There are several principles on which temperature sensor chips function. Infrared radiation sensor chips are based on the relationship between infrared radiation and infrared wavelength. Change of state due to heating is detected by change-of-state sensor chips. An RTD interface temperature chip is more accurate and more linear than thermocouples and is generally much more costly and slower responding. An RTD interface temperature chip is able to sense temperatures with good repeatability and low drift error from -200° C to 850° C. The fundamental design of a temperature semiconductor results from the fact that semiconductor diodes have temperature-sensitive voltage and current characteristics. A temperature IC can be analog or digital and both have several variations. The use of an IC temperature sensor is limited to applications where the temperature is within a - 55° C to 150° C range. The measurement range of an IC temperature sensor may be small as compared to that of thermocouples and an RTD interface temperature chip, but they have several advantages. For example, they are small, accurate, and inexpensive. With the higher level of integration now feasible, a digital IC temperature sensor can report both local and remote temperatures, monitor other system parameters, control fans, or warn when a specific temperature is exceeded. A computer temperature sensor helps in maintaining an appropriate environment inside a computer for proper functioning of all the hardware and protects it from being damaged. Temperature sensor chips are designed and manufactured according to various industrial specifications.

Applications

Temperature sensor chips are used in many applications. Some examples include personal computers, air conditioners, refrigerators, water heaters, microwaves, hot-wire anemometers, industrial instrumentations, and laboratory-quality measurements. Temperature sensor chips continue to evolve, providing a varied array of functions, features, and interfaces.

Temperature Sensor Chips FAQs

What are the key differences between thermocouples and thermistors in temperature sensing applications?

Thermocouples: Operate based on the Seebeck Effect, where a voltage is produced due to a temperature gradient between two different metals joined at their ends. This voltage correlates with the temperature difference between the thermocouple's two ends.

Thermistors: Are thermally sensitive resistors that change resistance with temperature variations. They can have either a negative temperature coefficient (NTC), where resistance decreases as temperature increases, or a positive temperature coefficient (PTC), where resistance increases with temperature.

Thermocouples: Suitable for a wide range of temperatures and are known for their adaptability and reliability in harsh environments. They are often used in applications requiring stability over time and adaptability to extreme conditions.

Thermistors: More sensitive to temperature changes than thermocouples, making them ideal for applications where detecting small temperature changes is important. However, they are not suitable for high-temperature applications due to their fragility.

Thermocouples: Commonly used in industrial, scientific, and commercial applications, including manufacturing, petrochemical processes, and HVAC systems. They are preferred for applications needing a broad temperature range and quick response times.

Thermistors: Best suited for applications requiring precise temperature control within a narrow range, such as in moderate temperature operations where reliability and safety are critical.

Thermocouples: Made from two different metals or metal alloys.

Thermistors: Typically composed of semiconductor materials or oxides of elements like cobalt, copper, and nickel. They have a higher resistance change per degree Celsius compared to RTDs, enhancing their sensitivity.

These differences highlight the suitability of thermocouples for broad and harsh temperature environments, while thermistors excel in precision within limited temperature ranges.

What is the Seebeck Effect and its role in thermocouples?

The Seebeck Effect is a fundamental principle underlying the operation of thermocouples. Here's a detailed explanation of the Seebeck Effect and its role in thermocouples:

The Seebeck Effect is the phenomenon where a voltage is generated across two dissimilar metals or semiconductors that are joined at two junctions when there is a temperature difference between these junctions. The hot junction is used for measuring the temperature and the cold junction is used as a reference temperature. This voltage is directly related to the temperature difference between the two junctions.

Mechanism: When two different conductive materials are connected at two points and exposed to different temperatures, electrons in the materials move from the hot junction to the cold junction. This movement of electrons creates an electromotive force (EMF), or voltage, which can be measured.

Temperature Measurement: In thermocouples, the Seebeck Effect is utilized to measure temperature. The voltage produced by the temperature difference between the two junctions of the thermocouple correlates with the temperature difference, allowing for precise temperature readings.

Applications: Thermocouples are widely used in various industrial, scientific, and commercial applications due to their ability to measure a broad range of temperatures and their reliability in harsh environments. They are particularly useful in manufacturing, petrochemical processes, HVAC systems, and scientific research.

Advantages: The use of the Seebeck Effect in thermocouples provides several advantages, including:

Wide Temperature Range: Thermocouples can measure temperatures across a wide range, making them versatile for different applications.

Durability: They are robust and can withstand harsh environmental conditions.

Quick Response: Thermocouples have a fast response time to temperature changes due to the low mass of the hot junction. This makes them suitable for dynamic environments.

What are the differences between thermocouples and RTDs?

Here are the key differences between thermocouples and RTDs (Resistance Temperature Detectors) in temperature sensing applications:

Thermocouples: Operate based on the Seebeck Effect, where a voltage is generated across two dissimilar metals when there is a temperature difference between their junctions. This voltage correlates with the temperature difference, allowing for temperature measurement.

RTDs: Measure temperature by correlating the resistance of the RTD element with temperature. Typically made from pure materials like platinum, RTDs have a predictable change in resistance with temperature changes.

Thermocouples: Can measure a wide range of temperatures, typically from -200°C to 2,500°C, making them suitable for high-temperature applications.

RTDs: Generally used for temperatures ranging from -200°C to 850°C. They are not suitable for extremely high temperatures compared to thermocouples.

Thermocouples: Generally less accurate than RTDs, with accuracy ranging from ±0.5°C to 5°C. They are also less stable over time, especially at moderate to high temperatures.

RTDs: Offer higher accuracy, typically within 0.1°C to 1°C, and provide more stable and repeatable measurements. They are less likely to drift over time.

Thermocouples: Have a faster response time due to their smaller size and construction, making them ideal for applications requiring quick temperature changes.

RTDs: Generally have a slower response time compared to thermocouples, but they provide more accurate readings.

Thermocouples: More durable in high vibration and mechanical shock environments. They are generally less expensive than RTDs, making them a cost-effective choice for many applications.

RTDs: More expensive due to their construction and materials. They are less durable in high vibration environments but offer lower long-term maintenance costs due to their stability and accuracy.

Thermocouples: Suitable for high-temperature industrial applications such as furnaces, gas turbine exhaust, and diesel engines.

RTDs: Preferred in laboratory and scientific applications, pharmaceuticals, and food processing industries where high accuracy and stability are crucial.

These differences highlight the suitability of thermocouples for high-temperature and dynamic environments, while RTDs excel in applications requiring precision and stability.

What are the typical applications for thermistors in industrial settings?

Here are the typical applications for thermistors in industrial settings:

Temperature Monitoring and Control

Thermistors are widely used in industrial heating applications where precise temperature control and monitoring are essential. They are particularly effective in maintaining reliability and safety in operations requiring moderate temperatures.

Automotive and Aerospace Industries:

In these industries, thermistors are employed for engine temperature monitoring applications. Their sensitivity to temperature changes makes them suitable for detecting small variations that can be critical in these environments.

Food Industry

Thermistors are used for temperature profiling in the food business, particularly in processing and cooking applications. Their ability to provide precise temperature control is crucial for ensuring food safety and quality.

General Industrial Applications

Due to their high sensitivity to temperature changes, thermistors are suitable for applications where minimal temperature changes are significant. However, they are not ideal for high-temperature applications due to their fragility.

These applications highlight the role of thermistors in providing precise temperature control and monitoring within specific temperature ranges, making them valuable in various industrial settings.

What are the advantages of using thermistors over other temperature sensors?

Here are the advantages of using thermistors over other temperature sensors, such as thermocouples and RTDs (Resistance Temperature Detectors):

High Sensitivity: Thermistors are more sensitive to temperature changes compared to thermocouples and RTDs. They exhibit a higher resistance change per degree Celsius, which makes them ideal for applications where detecting small temperature changes is crucial.

Precision: Thermistors provide precise temperature control and monitoring within specific temperature ranges. This makes them suitable for applications requiring high accuracy within a limited temperature range, such as in industrial heating and food processing.

Economical: While the documents do not explicitly compare the cost of thermistors to other sensors, their use in applications requiring precision within narrow temperature ranges suggests they can be a cost-effective choice for specific applications where high sensitivity is needed.

Versatile Materials: Thermistors are typically made from semiconductor materials or oxides of elements like cobalt, copper, and nickel. This composition contributes to their high sensitivity and allows for a range of temperatures and accuracies.

Specific Applications: Thermistors are particularly effective in applications such as automotive and aerospace engine temperature monitoring, and temperature profiling in the food industry, where precise temperature control is essential.

These advantages highlight the suitability of thermistors for applications requiring high sensitivity and precision within specific temperature ranges, making them valuable in various industrial settings.

What are the limitations of using thermistors in high-temperature applications?

Here are the limitations of using thermistors in high-temperature applications:

Thermistors are not ideal for high-temperature applications because they are fragile and can be easily damaged under such conditions. This fragility limits their use in environments where they might be exposed to high temperatures or mechanical stress.

Thermistors are generally suited for applications requiring precise temperature control within a narrow range. They are not designed to handle the broad temperature ranges that thermocouples can manage, which limits their applicability in high-temperature scenarios.

The materials used in thermistors, typically semiconductor materials or oxides, contribute to their high sensitivity but also limit their ability to withstand high temperatures. This makes them less suitable for applications that require durability at elevated temperatures.

These limitations highlight why thermistors are more commonly used in applications where precise temperature control is needed within a moderate temperature range, rather than in high-temperature environments.

Temperature Sensor Chips Media Gallery

References

Electronics360—Fundamentals of industrial temperature sensors

GlobalSpec—Comparing thermocouples versus RTD