What device is similar to an RTD but has a negative temperature coefficient?
a. Strain gauge c. Negative-type RTD b. Thermistor d. Thermocouple
The correct answer and explanation is:
The correct answer is b. Thermistor.
A thermistor is a type of temperature sensor that exhibits a negative temperature coefficient (NTC), meaning its resistance decreases as the temperature increases. This characteristic makes thermistors similar to Resistance Temperature Detectors (RTDs), which are also used to measure temperature by correlating changes in resistance. However, the key difference between thermistors and RTDs is that thermistors typically have a much higher sensitivity to temperature changes and are most effective over a narrower temperature range, usually from -50°C to 150°C.
RTDs, on the other hand, usually have a positive temperature coefficient (PTC), meaning their resistance increases with increasing temperature. They are commonly made of pure platinum and offer excellent accuracy and stability, making them ideal for high-precision temperature measurements. Thermistors, being made from ceramic materials like metal oxides, have a more nonlinear resistance-to-temperature relationship compared to RTDs, and their resistance change with temperature is much more pronounced.
Thermistors are widely used in applications that require precise and quick temperature changes, such as in medical devices, automotive sensors, and consumer electronics. Their ability to detect small temperature fluctuations makes them an excellent choice for applications where high sensitivity is needed over a limited temperature range. However, because of their nonlinear behavior and relatively limited temperature range, thermistors are typically not suitable for high-precision industrial applications where RTDs are favored.
In summary, thermistors are temperature sensors that function similarly to RTDs but have a negative temperature coefficient, and their resistance decreases as the temperature rises.