Thermistor
A thermistor is a type of resistor whose resistance varies with temperature. It is made from a metal oxide semiconductor material, usually manganese, nickel, or cobalt oxide, that exhibits a change in electrical resistance in response to a change in temperature. Thermistors are known for their accuracy and reliability and are used in a variety of applications including temperature measurement, thermal protection and control, energy management, and temperature compensation.
The thermistor was invented in the late 19th century by scientist Sir Charles Wheatstone, who intended to use it to measure changes in the temperature of a gas. Thermistors were widely used in the early days of electronics, before the invention of the transistor, and remain popular today due to their small size and low cost.
Thermistors are available in a variety of shapes, sizes, and types. One of the most popular types is the negative temperature coefficient (NTC) thermistor, which exhibits a decrease in resistance with an increase in temperature. These thermistors are primarily used in temperature sensing applications.
The resistance of an NTC thermistor is dependent on the temperature at which it operates. This relationship is manifested in the thermistor’s response curve, which is typically used to define the thermistor’s values. The most common type of thermistor is the two-terminal thermistor, which is formed from a semiconductor material that has been carefully manufactured for long-term stability and accuracy. The resistance of a two terminal thermistor is highly dependent on the environment it operates in.
The two-terminal thermistor is the most widely used type of thermistor due to its versatility. It is able to measure a wide range of temperatures, from subzero to well over 200 degrees Celsius. Furthermore, thermistors are available in a variety of versions and types for different applications. For example, a thermistor can be used to measure temperatures in explosive atmospheres, damp atmospheres, and environments with fluctuations in temperature. Additionally, thermistors are also used in medical applications, particularly in the measurement of body and tissue temperatures.
The accuracy of a thermistor is determined by its sensitivity and its temperature coefficient. A thermistor’s sensitivity rating is typically expressed as a “K” value and is measured in the units Kelvin per Watt. The temperature coefficient is the amount of resistance change (in ohms) per degree Celsius change in temperature. The higher the K rating, the more sensitive the thermistor and the greater the accuracy.
Thermistors are often used in combination with other components such as resistors, capacitors and diodes, to form a network of resistance and capacitance that is used in various applications including temperature regulation, thermostat regulation, and electrical motor control. Thermistors are also used in motor protection devices, surge protectors, and are widely utilized in instruments and measuring equipment since they offer excellent accuracy and reliability at a lower cost than other temperature sensing methods.
In conclusion, thermistors are widely used in various industries and applications due to their small size, low cost, and high accuracy. They are highly reliable and can measure temperatures over a wide range and can be combined with other components to form an accurate, reliable temperature sensing and regulating mechanism. Thermistors are often used in combination with other components in order to regulate temperatures in thermostats, motor control systems, and other applications requiring temperature accuracy.
