What is a Thermistor?
Thermistors are THERMally sensitive resISTORS whose electrical resistance varies predictably with their body temperature, making them ideal tools for monitoring and controlling temperature in numerous applications including household and industrial products. Thermistors are typically used in applications requiring accurate temperature measurements within the range of -55 to +300°C and are often used in demanding operational environments. The sensors can be provided encased in a probe assembly configuration, meaning they are mounted in a thermowell or protective housing made of metal or plastic to ensure they withstand the environmental stresses required by the application. Special insulated lead wires are offered as well.
EI Sensor offers a wide range of standard or off-the-shelf thermistors as well as custom designs to provide solutions to customers with unique requirements. If you have questions, click our handy list of key temperature sensor terminology or contact us.
How Does a Thermistor Measure Temperature?
Because thermistors have a very high and predictable change in their electrical resistance with temperature, simple circuitry can provide the user with accurate temperature measurements. Also, because of their high-temperature coefficient and unlike many other temperature sensors, lead wire length doesn’t significantly affect the accuracy of the measurement.
The Two Types of Thermistors
Thermistors come in two types. Negative-temperature-coefficient (NTC) thermistors decrease in electrical resistance as their body temperature rises and positive-temperature-coefficient (PTC) thermistors increase in electrical resistance as their body temperature rises.
Negative Temperature Coefficient (NTC) Thermistors
- NTC Thermistors are made of sintered metal oxides. The precise composition of the materials as well as the manufacturing process determines the resistance vs temperature characteristics of the product. NTC thermistors are most useful in applications requiring precision temperature measurement and/or control and can withstand operating temperatures from -55°C to +300°C.
Benefits
- High Sensitivity: NTC thermistors respond quickly to temperature changes, providing accurate readings essential for precise control in various applications.
- Wide Temperature Range: They function effectively across a broad range of temperatures, making them versatile for many environments.
- Cost-Effective: Compared to other temperature sensors, NTC thermistors offer an affordable solution without compromising performance.
- Compact Size: Their small size allows them to be used in tight spaces, making them ideal for modern electronic devices.
- Reliability: With robust and stable performance, NTC thermistors ensure consistent operation over time, reducing maintenance needs.
These attributes make NTC thermistors a preferred choice in applications like HVAC systems, automotive sensors, and household appliances.
Positive Temperature Coefficient (PTC) Thermistors
- PTC thermistors increase their electrical resistance as the temperature increases. Two types of PTC thermistors are Switching PTCs which are non-linear ceramic sensors and Silicon PTCs which exhibit a nearly linear positive ~7,000 ppm temperature coefficient of resistance. Switching PTCs are produced using polycrystalline ceramic materials such as barium carbonate and titanium oxide while Silicon PTC thermistors rely on the bulk resistance properties of doped silicon.
Benefits
- Overcurrent Protection: PTC thermistors act as self-resetting fuses, protecting circuits from overcurrent conditions without needing replacement.
- Temperature Regulation: They are ideal for maintaining consistent temperatures in heating elements and thermal management systems.
- High Reliability: PTC thermistors are durable and provide stable performance, ensuring reliable operation in critical applications.
- Fast Response Time: Their quick response to temperature changes helps prevent damage in sensitive electronic components.
- Easy Integration: With simple and compact designs, PTC thermistors can be easily incorporated into a wide range of electronic devices.
These advantages make PTC thermistors an excellent choice for applications like motor protection, surge current limiting, and as heating elements in automotive and consumer electronics.
What are the Applications of NTC Thermistors?
NTC thermistors are widely used in everyday life from HVAC applications such as room thermostats, pool and spa controls, air conditioners, and heating systems to appliances such as refrigerators, ovens, and washing machines. They’re also commonly used in aerospace applications. Due to their excellent accuracy as well as long-term reliability, NTC thermistors are the sensor of choice for temperature measurement and control.
NTC thermistors are often used in harsh environments, so EI Sensor offers thermistor probe assemblies that combine a thermowell or probe assembly as well as specialized lead wires appropriate for each application. Click to learn more about EI Sensor thermistor probes.
What are the Applications of PTC Thermistors?
PTC thermistors are most often used for self-resetting overcurrent protection in small DC motors and as self-regulating spot heaters. You will commonly find PTC thermistors in household appliances that generate heat, automobiles, and many other household and industrial applications.
Looking for Thermistors? Contact Us Today!
EI Sensor offers a range of standard and custom thermistors. If you have questions about which of our standard products will perform best in your application, contact us, and we’ll be happy to help. We are also pleased to support customers whose unique temperature measurement requirements may need a custom solution.
EI Sensors are available and used worldwide, including through our distribution partners.