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Knowing how to prevent your electronic devices from overheating can help to avoid dangerous incidents such as electric shock, explosion or even data loss. The overheating is sometimes caused by short circuits, mishandling of electronics and use of inappropriate Negative Temperature Coefficient (NTC) thermistors.
An NTC thermistor is a heat-sensitive resistor which regulates the temperature in devices thus enabling them to work efficiently.
Fortunately, you can guarantee your own safety and the optimal performance of the electronics by leveraging the information contained in this article.
Read on to discover why NTC thermistors are indispensable and how to pick the most suitable one for your specific applications.
Why Should You Choose The Right NTC Thermistor?
But before we get started, it’s good for you to know from the onset why the right NTC thermistor matters. Here are three key reasons that underline why you should make the correct choice:
Safety
- The right NTC thermistor can quickly identify fluctuations in temperature. As a result, it would be possible to act swiftly as the occurrence would be detected early.
- Conversely, the wrong one may give inaccurate readings causing uneven temperature control or system failure. Imagine what would happen if, for instance, the wrong NTC thermistor was installed in a fire alarm system.
- A sudden change in temperature would be undetected. A fire would probably break and go unnoticed until too late.
Optimal Performance
- The appropriate selection of an NTC thermistor guarantees the efficient operation of your system or device. This is because it’s capable of rapidly responding to temperature fluctuations. A perfect example of this is the light-emitting diodes (LEDs) commonly used in different lighting applications.
- The LEDs produce a great deal of heat which can impact their brightness and lessen their lifespan. With the right NTC thermistor, the temperature is lowered enabling LEDs to function at full capacity.
Energy Efficiency
- A good NTC thermistor improves the efficient use of energy through precise control of temperatures. This not only lowers the energy costs but also prolongs the lifespan of the device or equipment.
- Additionally, the proper thermistor reduces the possibility of breakdown and guarantees effective operation. Consequently, it minimizes maintenance expenses and enhances general reliability in the long run.
What Are the Main Types of NTC Thermistors?
The operating principle of NTC thermistors is that their resistance decreases as the surrounding temperature increases. In other words, they exhibit a negative correlation between electrical resistance and temperature. Hence their name Negative Temperature Coefficient thermistors.
The most common types of NTC thermistors are follwing:
Let’s explore their features.
Disco y chip
Its surface contact is made from metal oxide ceramic material. Disc thermistors are larger and thicker in size than other NTC thermistors which makes their reaction time comparatively slower.
However, this gives them a greater dissipation constant. Simply put, they need more power to raise the temperature of the thermistor by 1°C above the normal temperature. This means that they can handle greater currents far better than the epoxy-coated thermistors.
This type of thermistors are characterized by their compact and slim design. They are usually affixed to the surface of printed circuit boards. They exhibit a quicker response time and demonstrate heightened sensitivity to variations in temperature. However, their limitation is that their resistance changes in a non-linear manner at temperatures below 0°C and above 70°C.
Características
- High Sensitivity: Provides accurate measurement results
- Fast Response Time: They can make temperature adjustments instantly.
- Wide Range of Resistance Values: Suitable for any type of task and structure.
- Compact Size: The small construction makes these thermistors suitable for most electronic devices.
Solicitud
Its compact design makes it easy to integrate into a variety of applications as described below:
- Electronic Assemblies – Audio and video systems such as color TVs, DVD players and loud speakers.
- Electrodomésticos – Refrigerators, washing machines, hair dryers and ovens.
- Computerized Systems – Computers, smartphones and iPhones.
- Medical Devices – Catheters, dialysis and surgical equipment.
Epoxy Thermistor
These are epoxy-coated NTC thermistors whose protective layer enhances their functionality and endurance.
However, these thermistors are appropriate for low-temperature measurement ranges, as the layer is unsuitable for high-temperature applications.
Características
- Durable Encapsulation: It provides the necessary resistance to moisture and mechanical stress resistance.
- High Sensitivity: Offer accurate temperature readings with significant resistance changes.
- Compact Design: Its integration is quite flexible and can be incorporated in different systems.
- Fast Response Time: These provide excellent solutions for uses where quick temperature adjustments are needed.
Solicitud
Due to their encapsulation, epoxy coated thermistors are suitable for use in low-temperature applications where moisture is present. These include industrial and automotive applications.
Epoxy thermistor in the car that enables you to control air conditioning and warm the seat for passenger cabins. It also help to monitor the temperature of exhaust gas, cooling oil and water, and the braking system.
Glass-Encapsulated
Unlike the epoxy coated ones, this type of NTC thermistor are designed to withstand high temperatures.
The glass coating protects against environmental factors such as dust, chemicals and moisture penetration. This guarantees stability and an error-free resistance reading.
Características
- Robust Protection: The glass encapsulation protects them from external elements and enhances their durability.
- High Precision: They provide correct temperature readings with a low degree of variation in a given period.
- Wide Temperature Range: Useful for extreme temperature conditions, from very cold or very hot conditions.
- Stable Performance: Maintain high accuracy and consistency in varying conditions.
- Compact Size: It’s flexible and fits easily into tight spaces in your e
Solicitud
Glass-encapsulated NTC thermistors are used in a variety of applications including:
- Digital thermostats,
- Over-current protection,
- Uninterruptible power supplies (UPS) and
- Thermometers.
Conjuntos de sondas
These are specialized temperature sensors designed for direct temperature measurement across various applications.
They are housed within a casing which protects the thermistor from physical damage. There are various sizes and materials, making them adaptable to different mounting requirements.
Características
- Customizable Probes: They come in various lengths and can be made using various material types.
- High Sensitivity: Can respond to temperature changes immediately for monitoring purposes.
- Robust Construction: Often built to withstand harsh environments and mechanical stress.
- Versatile Compatibility: It can be easily integrated with other systems. In addition, you can use them independently as sensors.
Solicitud
Commonly used in medical devices, green energy, heating ventilation air conditioning systems, and industrial applications.
- Medical Devices – During the Covid-19 pandemic these probes played an important role in enabling patients to breathe through ventilators. Since the patients’ respiratory system had failed, so the thermistor need to be accurate and help regulate the body temperature to roughly 37°C.
- Green energy – In wind turbines, these thermistors are crucial in measuring the temperature of blades in a cold environment. In extremely low temperatures, the blades may freeze rendering the turbine inoperable. To prevent this, the thermistor signals the turbine’s heater to compensate for the low temperature.
Montaje en superficie
Their small size allows for seamless integration into space-constrained electronic designs, typically mounted directly on the surface of a printed circuit board.
Owing to their compact structure, they offer rapid response times and effective thermal coupling especially in tightly confined settings.
Características
- Fast Response Time: They offer a quick response to temperature changes for appropriate monitoring.
- Wide Range of Values: Come in various resistance values and have different temperature coefficients depending on the application.
- Low Thermal Mass: This feature helps make them appropriate for dynamic systems as they proactively respond to any change in temperature.
- Reliable Performance: Designed for durability and consistent readings over time
Solicitud
Surface mount NTC thermistors are used in:
- Portable media devices – Smartphones, tablets, and laptops.
- Home appliances – Ovens and refrigerators
- Medical equipment – thermometers, catheters and glucose monitors.
- Car manufacturing – Cabin temperature and battery monitoring.
Key Selection Criteria for NTC Thermistors
When choosing a suitable NTC thermistor, it is essential to take into account various factors. Each of these criteria plays a significant role in comprehending the thermistor’s subsequent performance in your specific environment.
6 Essential Considerations When Selecting NTC Thermistors
The following are 6 key considerations to keep in mind when choosing an NTC thermistor:
Rango de temperatura
Its function smoothly within a temperature spectrum of between -50°C and 250°C. Therefore, it is crucial that put the determination of temperature range before selecting the NTC thermistor.
Ascertain that the thermistor shows both the lowest and highest functional temperatures. This is especially important because the thermistor’s temperature range determines its suitability and lifespan in a particular application.
Exactitud
The NTC thermistors’ accuracy falls within a range of between 0.05°C and 0.20°C. For correct measurements, this accuracy should remain stable across a wide temperature range.
Precise measurements provide you with definitive data thus ensuring your system’s efficiency. Some of the best illustrations of this include medical devices, also cooling and heating systems.
Further, ensure that you check the specifications for the thermistor’s sensitivity and tolerance.
Estabilidad
A thermistor’s stability is a crucial factor for its extended performance. The stability can be reduced significantly by elements such as drift in the resistance and aging.
It is important to have a thermistor that has been tested for stability under various environmental conditions. Having a stable thermistor means you won’t have to recalibrate or replace it for a long while.
Embalaje
The conditions to which the thermistor will be exposed such as moisture and extreme temperatures determine its packaging. Earlier on, we highlighted the different types of thermistors including disc, chip, epoxy, and glass seal types.
Let me illustrate why packaging is important: in a year, a hermetically-sealed thermistor can fluctuate by only 0.02°C whereas the epoxy-coated one can change by 0.2°C within the same period.
Choosing the right packaging enhances the thermistor’s performance in its specific application.
Inmunidad al ruido
This is a crucial factor to consider particularly in environments where there is electromagnetic interference. An NTC thermistor ought to operate well in such an environment.
When selecting a thermistor, check the device’s noise immunity specifications. This quality is especially useful in telecommunication, industrial applications and other environments where electromagnetic interference is common.
Power Dissipation
The NTC thermistors can dissipate only a limited quantity of power. If the dissipated power exceeds the dissipation constant of the temperature sensor, there is a high likelihood that the thermistor will self-heat. This can lead to inaccurate measurements.
For example, if a selected thermistor has a thermal coefficient of 5 milliwatts per degree Celsius (mW/°C) and the device dissipates a power of 20mW/°C, the effect of self-heating will produce an error of 4°C.
Therefore, ensure there is a match between the capacity of a thermistor’s power dissipation and the thermal needs of your application.
Solicitud
Probe assemblies NTC thermistors are commonly used in medical devices, green energy, heating ventilation air conditioning systems, and industrial applications.
- Medical Devices – During the Covid-19 pandemic they played an important role in enabling patients to breathe through ventilators. Since the patients’ respiratory system had failed, the thermistor had to be accurate and help regulate the body temperature to roughly 37°C.
- Green energy – In wind turbines, these thermistors are crucial in measuring the temperature of blades in a cold environment. In extremely low temperatures, the blades may freeze rendering the turbine inoperable. To prevent this, the thermistor signals the turbine’s heater to compensate for the low temperature.
More Considerations When Selecting NTC Thermistors
Besides these primary criteria, you need to consider a few other factors. Knowledge of these considerations will assist you in making the right decision Here are some additional aspects to consider:
Thermal Time Constant (T.C.)
The thermal time constant (T.C.) is an indication of a thermistor’s ability to react to temperature variations. It is the time required for a thermistor to register 63.2% of the total variation between the initial and final temperature.
A shorter T.C. means a faster response. At the same time, a larger thermistor will have a slower response time. Therefore, carefully consider the appropriate thermistor type and the necessary response time that meets your application’s needs.
Resistor Value Selection
Choosing the right resistor value is crucial for both sensitivity and accuracy. The resistance directly influences the performance and response time of the thermistor.
It is essential that you align the resistor value with the specific requirements of your application. Additionally, take into account factors such as the operating temperature when making your selection.
R-T Curve Selection
The R-T curve illustrates the relationship between a thermistor’s resistance and temperature. Each thermistor has a unique R–T curve.
Examine the graph to determine whether the temperature range of your application falls within the specified limits. Consequently, selecting a thermistor with the right characteristic curve in the R-T parameter is crucial.
Tolerance
Tolerance is the permissible variation in the resistance of a thermistor. It is essential to achieve measurement accuracy in accordance with the specific requirements of the application.
A lower tolerance indicates greater precision, making it suitable for sensitive applications.
What Are the Main Application Fields of NTC Thermistors?
As previously mentioned, NTC thermistors are applicable to many electronic appliances and devices. Here’s an overview of some of the applications:
Cómo se aplican los termistores NTC en vehículos eléctricos
NTC thermistors play a crucial role in electric vehicles by monitoring and regulating the temperature of batteries.
Their primary function is to prevent the battery temperature from reaching hazardous levels, thereby ensuring safety. The thermistors are therefore essential for enhancing the longevity and efficiency of batteries.
How NTC Thermistors Are Applied Home Appliances
Various types of NTC thermistors are extensively utilized in numerous home appliances to detect and control temperature. For example, in refrigerators they ensure proper internal temperatures by measuring the ambient temperature within the unit.
Conclusión
Having the appropriate NTC thermistor ensures optimal performance of your device. It can also extends the lifespan and reduces energy costs. More importantly, it guarantees your personal safety.
Selecting the suitable thermistor for your application isn’t difficult. Whether you want the right thermistor for your car or coffee maker, we are here to guide you. There are continuous customer support and offer free consultation. It’s our honor to provide a satisfactory experience.
If you have any more questions, feel free to contact us. It’s a good choive to view our catalog of thermistors on DTTTEK.
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