What is NTC Thermistor

• FIG1. As in Fig., a sensor whose resistance changes when the temperature rises is called a thermistor.
• There are NTC thermistors with negative (-) temperature coefficients, PTC thermistors with (+) temperature coefficients, and CTR thermistors with rapid changes in electrical resistance at certain temperatures.Among them, NTC thermistors (Negative Temperature Coefficirent of Resistor) are mostly used at an operating temperature of less than 300°C, mixing two or more types of transition metal oxides such as Co, Mn, Ni, Cu, and Fe, and using CuO and resistance values to improve sinterability. By adding F₂O₃ or Lio₂ to reduce the resistance and Cr₂O₃ to increase the resistance value, the sintered compact at high temperature of 1200~1400℃ has a stable spinel structure or rock salt structure, so the resistance is Themally Sensitive with a (-) temperature coefficient is a resistor.

• The NTC thermistor has been continuously researched since Faraday discovered the NTC characteristic at the end of the 18th century, and after a patent application for Mn-Ni-Fe-based oxide was applied at Bell Labs in 1939, the NTC thermistor was first commercialized for temperature compensation of a transistor receiver circuit.
• From the Second World War to the present, depending on the temperature of use, Mn-Co-Ni-Fe system was used for low temperature, and Al, Zn, Mg, Cr, etc. were added to Co-Mn system for high temperature, or CeO2-ZrO2 system was used. have.
• At this time, the characteristic of the thermistor is that the resistivity at room temperature is 10-2~10-4 Ω∙cm, the B constant is about 2000~10000K, and the temperature coefficient α is -3~-6%/℃. The shape is developed and used from the DISK type to the integrated electrode. The size is 1.5*1.5*0.5mm for a square chip, and for a disk type, the outer diameter is 2-3mm or less, and the temperature accuracy is ±1℃ to ±0.2℃, The resistance value and the B constant value are required to be precise from ±5% to ±1%, and the responsiveness of the chip type is also increasing gradually to about 1~3sec.
• In recent years, many researchers have expanded the range of applications by stabilizing the device itself, achieving high precision and miniaturization.

General Characteristics of NTC Thermistor

• 01. Measurement of very small temperature and precision measurement is satisfactory because resistance temperature coefficient regarding temperature is large.

• 02. Miniaturization is possible due to simple composition.

• 03. Has no contact point, allowing high reliability and low change over time.

• 04. Insensitive to pressure, magnetic force, and other factors.

• 05. Great for mass production, allowing mass supply at stable price.

• 06. Great mechanical strength and processability.

• Used widely in electronic appliances, OA instruments, cars and industrial equipment, utilizing the above characteristics for measuring and controlling temperature, for characteristic compensation and for circuits, and for measuring and controlling things other than temperature.
• Also, recently, it is being used for special purposes such as measuring humidity or meteorological observation.

Uses of NTC Thermistor

• Thermistor is used in all fields related to temperature, thus is used in large quantity in temperature measuring equipment, and temperature control and detection equipment, and in particular is widely used for cooking purposes (microwave oven, electric rice cooker etc.), air adjuster, air-conditioning/heating element, office equipment (copier, printer etc.), electrical car parts, industrial, service instruments, health supplication equipment, beauty instruments, farmingㆍindustrialㆍfishery equipment, medical equipment, physio-chemical instruments, and general measuring instruments etc.