Thermistors
A thermistor is a type of temperature sensor that is a thermally sensitive resistor. Its resistance changes with temperature, making it a valuable tool for temperature measurement and control. Two primary types of thermistors exist, characterized by the way their resistance responds to temperature changes: Positive Temperature Coefficient (PTC) thermistors and Negative Temperature Coefficient (NTC) thermistors.
An NTC thermistor is known for its property where resistance decreases as the temperature increases. Conversely, a PTC thermistor's resistance increases as the temperature rises. When we delve into the specifics of the negative temperature coefficient, the term essentially implies that as the ambient room temperature goes up, the NTC thermistor's resistance will drop. This characteristic makes NTC thermistors especially valuable for measuring temperature in various applications.
PTC thermistors, on the other hand, are quite the opposite. When the temperature rises, the positive temperature coefficient ensures that the resistance of the PTC thermistor also goes up. PTC thermistors are often utilized in protection circuits and situations where there's a need to react to higher temperatures.
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The temperature range in which a thermistor operates can vary. While some are designed for a limited temperature range, others can handle a broader span of temperatures, from very high temperatures to cooler ones.
Beyond mere temperature sensing, thermistors play a role in temperature control systems. For instance, a temperature controller might monitor the resistance of a thermistor to maintain a constant temperature. In scenarios where maximum surface contact is essential, such as body temperature monitoring, surface-mounted thermistors can be employed.
In the world of temperature sensors, there are other devices like resistance temperature detectors and integrated circuits. However, thermistors stand out due to their high sensitivity to temperature changes and their ability to provide accurate temperature readings even in extreme temperatures. They are commonly made of metal oxides, which contribute to their unique properties.
FAQs
What is positive temperature coefficient resistance?
Positive Temperature Coefficient (PTC) resistance refers to the property of certain materials where their electrical resistance increases as the temperature rises. In other words, when a material with a PTC characteristic is heated, it becomes less conductive.
Can thermistors measure oil and coolant temperatures?
Yes, thermistors can measure oil and coolant temperatures. In fact, they are often used in automotive and industrial applications for this exact purpose.
What is a Thermistor?
What is a Thermistor?
Thermistors are thermally sensitive resistors that rely on the change in electrical resistance to measure temperature. As the temperature changes, the resistance changes. The resistance of a specific thermistor will equal a certain temperature based off of the scaling for that device. There are two different styles of thermistor that can be used. The Negative Temperature Coefficient (NTC) and the Positive Temperature Coefficient PTC). NTC thermistor's resistance decreases with the increase in temperature. PTC thermistor's resistance increases when the temperature increases.
What are the advantages and disadvantages of a thermistor compared to an RTD?
Thermistors are less expensive than RTDs and are able to measure temperature changes faster due to their smaller size. They can provide more resolution or better accuracy within the range that they are rated to measure. However, the temperature range is more limited compared to RTDs. Anything higher than 350 degrees Celsius would all but eliminate a thermistor as a good option.