Thermocouples, resistance thermometers, NTC thermistors

Temperature sensors are used to stop temperature measurement. Although they are numerous, in practical use, thermocouples, resistance thermometers, and NTC thermistors are the most commonly used temperature sensors. Below is a detailed introduction to these three types of temperature sensors.

1. Thermocouple: Composed of two dissimilar metal wires welded together to form two junctions. The temperature difference between nodes will generate thermoelectric potential (i.e. voltage) between two wires. By maintaining the reference node at a known temperature and measuring the voltage during the process, the temperature of the detection node can be inferred. The advantage of thermocouples is that they have a wide range of task temperatures and a small body size. However, they also have disadvantages such as low output voltage, susceptibility to noise from wire loops, and high drift.

2. Resistance thermometer (RTD)

It is a coiled wire or thin film spiral tube that may exhibit changes in resistance value with temperature. Although commonly used metals include copper, nickel, and nickel iron alloys, RTDs made of platinum exhibit linearity, repeatability, and stability. Relying on its excellent linearity

With the temporary stability of *, the platinum RTD firmly established its position as a temperature reference scale for me. Although thin-film platinum RTDs provide functional matching, scale grade wire wound resistors are superior in terms of cost, shape, size, and convenience. Late stage thin-film platinum RTDs are plagued by drift due to their high nominal volume to volume ratio, making them increasingly sensitive to infection. Afterwards, the improvement of film cutting and packaging eliminated these achievements, making film RTD surpass wire wound resistors and NTC thermistors and become a temperature sensor.

3. NTC thermistor

Composed of metal oxide ceramics, it is a low-cost and highly sensitive temperature sensor. At the same time, they are also temperature sensors with linear differences and have negative temperature coefficients. Thermistors have various shapes and sizes, base resistance values, and resistance temperature (R-T) function correlation curves, which can be used for simplifying packaging and output linearization circuits.