Thermistors – find manufacturers and suppliers

Thermistors are temperature-dependent, electrical semiconductor components that significantly change their electrical resistance in the event of temperature changes.

This change in resistance is evaluated by downstream electronics and used to display or control the temperature. They are often used as temperature sensors or to limit the current in electronic circuits.

Below is an overview of how thermistors work, their types and applications, as well as an overview of their properties:

How thermistors work:

Thermistors, derived from "thermal resistors", are temperature-dependent electrical resistors. Their electrical resistance changes significantly with temperature. Thermistors consist of semiconducting materials (e.g. metal oxides) whose conductivity is strongly temperature-dependent.

1. In NTC thermistors, which are made of semiconductor materials with many charge carriers, additional electrons or holes are released when the temperature increases. This results in higher conductivity and therefore lower resistance.
   They are ideal for precise temperature measurement because the change in resistance is strong and reproducible.
2. PTC thermistors conduct relatively well at low temperatures. Above a certain temperature, the switching temperature or Curie temperature, the crystal structure or the doping properties change. This results in a sudden deterioration in conductivity, i.e. an increase in resistance.
   This property is used as a self-healing fuse or as a soft-start limiter for motors or power supply units.

Both properties are also used to measure temperatures, detect temperature changes or control or protect circuits depending on temperature.

Types of thermistors:

1. NTC thermistors (Negative Temperature Coefficient):
   With these, the resistance decreases as the temperature increases.
   They are widely used in temperature measuring devices, e.g. in digital thermometers, as temperature sensors in air conditioning systems and refrigerators, as well as for monitoring the temperature in batteries and electronic devices.
2. PTC thermistors (Positive Temperature Coefficient):
   With these, the resistance increases significantly with increasing temperature.
   They are often used for overcurrent protection and temperature compensation, for example in power supply units, overload protection switches and heaters.

Applications of thermistors:

1. Temperature sensors:
Thermistors are used in thermometers, air conditioners, refrigerators and other appliances to measure and control temperature.

2. Overcurrent protection:
PTC thermistors serve as self-healing fuses. If the current gets too high, their temperature rises and so does their resistance, which limits the current flow.

3. Temperature compensation:
They compensate for temperature dependencies in electronic circuits, for example in oscillators or in measurement technology, where temperature-related fluctuations are undesirable.

4. Battery protection:
In rechargeable batteries, thermistors can monitor the temperature and prevent overheating by adjusting the charging system accordingly.

5. Starting current limitation:
In power supplies and motors, NTC thermistors prevent excessive current from flowing when switched on by initially providing a high resistance that decreases as the temperature rises.

Properties of thermistors:

• Thermistors respond quickly to temperature changes, making them useful for real-time monitoring and protection applications.
• NTC thermistors in particular offer high sensitivity to temperature changes, which enables precise measurements.
• They are small and inexpensive, making them suitable for a wide range of applications.

Thermistors are important components in electronics due to their versatility, low cost and reliability.

Here is an overview of the most important criteria to consider when buying thermistors:

When buying thermistors, you should consider several factors to ensure they are suitable for your application.

• Choose an NTC thermistor if you need a sensor for temperature measurement, temperature monitoring or to limit the starting current. They have a negative temperature coefficient (resistance decreases with increasing temperature).
• Choose a PTC thermistor if you have an application for overcurrent protection or temperature compensation. They have a positive temperature coefficient (the resistance increases as the temperature rises).
• Pay attention to the operating temperature range of the thermistor. This should cover the temperature values that can occur in your specific application. Thermistors have different specifications, which can vary depending on the ambient temperature (e.g. -40°C to +125°C or -55°C to +150°C).
• The nominal resistance (often specified at 25°C, therefore also referred to as R25) is a critical parameter. Make sure that the resistance value matches the desired measuring range and the electrical circuit. Typical values range from a few ohms to several megaohms.
• Check whether additional requirements such as self-calibration, protective coatings or special connection options are needed.
• The tolerance of the resistance (e.g. ±1%, ±5%, ±10%) indicates how accurate the actual resistance value of the thermistor is at the reference temperature. For precise measurements, select a lower tolerance.
• The B value or temperature coefficient indicates how much the resistance of the thermistor changes per temperature change. A high B value means a greater change in resistance per degree Celsius. This value is important for the accuracy of the temperature measurement and should match the desired application.
• Thermistors are available in various designs (e.g. wired, SMD, with housing). The choice depends on the mechanical and thermal installation situation:
• Wired thermistors are well suited for measuring applications or at high temperatures.
• SMD thermistors are suitable for compact and automated applications on printed circuit boards.
• Various housing variants offer additional protection in harsh environments.
• The response time of the thermistor is important for applications that need to detect rapid temperature changes. Smaller designs and materials such as glass or ceramic enable faster response times.
• Pay attention to the load capacity (power limit) to ensure that the thermistor will not be damaged under the given current or voltage load. also check the long-term stability, especially for applications where the thermistor must operate constantly over long periods of time.
• Take into account special environmental conditions such as humidity, chemical stress, vibrations or mechanical shocks that may affect the thermistor. Select robust and resistant types accordingly.
• Consider the cost and availability of the thermistors, especially for projects with high quantity requirements or long-term applications. Sometimes specialized types are more expensive or harder to obtain.
• Check whether the manufacturer meets certifications such as ISO 9001 or relevant industry-specific standards.

By considering these factors, you can ensure that the thermistor is suitable for the specific requirements of the application and will perform reliably.

Thermistors can be purchased from various suppliers. Comprehensive information about manufacturers and suppliers of Thermistors from all over the world can be found on Exportpages.