Introduction to Thermistors
A thermistor is a 2-terminal electronic component that utilizes its resistive properties to measure temperature changes. Unlike simple resistors, the resistance of a thermistor changes in a predictable manner with variations in temperature. This makes it an essential tool in temperature sensing applications across various industries.
How Thermistors Work
A thermistor is essentially a solid-state semiconductor device. When the temperature around the thermistor changes, so does its electrical resistance. Specifically, a thermistor has a resistance that falls as the ambient temperature rises, which forms the basis of its temperature measurement capabilities.
This unique property of thermistors makes them indispensable in electronic circuits where precise temperature control and measurement are required. They can be used in a wide range of applications, from simple home appliances to complex industrial equipment.
Types of Thermistors
Thermistors can be classified into two main types based on their temperature coefficient: positive temperature coefficient (PTC) and negative temperature coefficient (NTC).
Positive Temperature Coefficient (PTC) Thermistor: The resistance of a PTC thermistor increases as the temperature increases. These are typically used for over-temperature protection and circuit control applications. Negative Temperature Coefficient (NTC) Thermistor: In contrast, an NTC thermistor’s resistance decreases with an increase in temperature. NTC thermistors are predominantly used in temperature measurement and compensation.Practical Applications of Thermistors
One of the primary applications of thermistors is in electronic thermometers. They provide a reliable and accurate means of measuring temperature, often in conjunction with other circuit components to enhance the sensitivity and response time.
Thermistors can also be used in series with other resistors to stabilize circuits. By carefully selecting the values, these components can work together to maintain a stable voltage across the circuit even when the ambient temperature changes.
A more innovative application of thermistors can be found in experimental avionics. In the 1980s, they were used in the design of a low-cost electro-fluidic autopilot for experimental homebuilt aircraft. By passing a linear stream of air between two thermistors and rotating the aircraft, the change in airflow would cool one thermistor compared to the other, providing a directional reference for the autopilot system.
Temperature Sensing and Precision
The key to effective temperature sensing using thermistors lies in the precision of their resistance-temperature relationship. In order to get the most accurate readings, it is crucial to avoid measuring the resistance with a current large enough to heat up the thermistor. Instead, precise voltmeters are often used to measure the minute changes in voltage across the thermistor, particularly when it is deployed in a stable temperature environment.
By properly incorporating thermistors into electronic circuits, engineers can achieve highly accurate temperature measurements with minimal error. This is especially useful in applications where precise temperature control is critical, such as in laboratory settings, HVAC systems, and medical devices.
Conclusion
In summary, thermistors are versatile and precise temperature sensing devices that have found myriad applications in modern electronic systems. Whether used in basic temperature measurement or more complex control systems, the unique properties of thermistors make them an indispensable component in the world of electronics and beyond.
References
Keating, Michael. (n.d.). What does a thermistor measure? [Answer]. Retrieved from [Source URL]