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Difference Between Thermistor and RTD
Thermistors and RTDs (Resistance Temperature Detectors) are two types of temperature sensors that work on the principle that electrical resistance changes as temperature increases. They differ, however, in terms of construction, materials, and temperature ranges.
Read this article to find out more about Thermistors and RTDs and how they are different from each other.
What is Thermistor?
A thermistor is a type of temperature sensor that works on the principle of electrical resistance changing with temperature. It is made from a semiconductor material, usually ceramic or polymer, and has a negative temperature coefficient (NTC), which means its resistance reduces as the temperature increases.
Thermistors come in a variety of shapes and sizes, including beads, discs, rods, and chips. They are also available in a variety of resistance values, with common resistance values ranging from 1 to 100 k. The selection of a thermistor depends on the application's specific needs, such as temperature range, precision, and response time.
Thermistors are classified into two types: negative temperature coefficients (NTC) and positive temperature coefficients (PTC). An NTC thermistor has resistance that reduces as temperature rises, whereas a PTC thermistor has resistance that rises as temperature rises.
One of the primary advantages of thermistors is their high sensitivity to temperature fluctuations. As a result, they are valuable in applications where small temperature changes must be detected, such as medical devices, automotive systems, and industrial processes.
What is RTD?
An RTD, or Resistance Temperature Detector, is a temperature measuring electrical device. It is a sort of temperature sensor that operates on the concept of electrical resistance variation with temperature. RTDs are widely used in a variety of industries, including aerospace, automotive, chemical, and food.
An RTD's basic operation is based on the fact that the electrical resistance of a conductor increases with temperature. This resistance variation can be monitored and correlated to temperature. RTDs are usually made of platinum, nickel, or copper wire wound around a ceramic or glass core. Because of its great stability and linear response to temperature fluctuations, platinum is the most often used material for RTDs.
RTDs come in a variety of resistance levels and temperature coefficients, allowing for a wide range of temperature measurements. RTDs with a resistance of 100 ohms at 0 °C and a temperature coefficient of 0.00385 ohms/ohm/°C are commonly used.
The main advantages of using RTDs for temperature measurement are their great precision, stability, and dependability. They also have a wide temperature range and are stress- and vibration-resistant.
Difference between Thermistor and RTD
The following table highlights the major differences between Thermistor and RTD −
Characteristics |
Thermistor |
RTD |
|---|---|---|
Type |
NTC or PTC |
Usually platinum |
Resistance |
It varies with the temperature. |
It increases with the temperature. |
Temperature Range |
-100 to +300 °C |
-200 to +850 °C |
Accuracy |
Moderate to high |
High |
Linearity |
Non-linear |
Linear |
Stability |
Moderate to high |
High |
Response Time |
Fast |
Moderate to slow |
Self-heating effect |
Significant |
Negligible |
Cost |
Low |
High |
Use cases |
General purpose |
High-precision |
Conclusion
In conclusion, thermistors and RTDs are two types of temperature sensors that work on the basis of variations in electrical resistance with temperature. While both sensors are suitable for temperature monitoring, they differ in their structure, materials, temperature ranges, accuracy, and reaction times.
Thermistors are small, fast, and inexpensive sensors that are good for temperature sensing in small spaces, whereas RTDs are larger, more expensive, and more precise sensors that are suitable for high-precision temperature measurement in a wide range of applications.
The decision between these sensors depends on the application's specific requirements such as temperature range, precision, response time, and cost.
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