posistor
PTC resistor (RTS thermistor) is an electronic component that has a positive resistance coefficient and performs dual functions: a heater and a temperature sensor. When high voltage or current is applied, the electronic component becomes hot. The higher the temperature becomes, the more its internal resistance increases, which means less current will flow through the element. Heating of the RTS component can occur under the influence of the external environment. In this case, it works as a temperature sensor.PTC resistors have a housing design in the form of round washers filled with enamel, or in the form of ceramic elements sequentially installed in a single housing.
In the diagram, the posistor has the following designation:
Application of a posistor
Since the posistor is a fairly accurate component, its scope of application in radio electronics is as follows:- protection of primary circuits of transformer windings;
- efficient current starter for electric motors;
- current limiter in heating devices (soldering irons, glue guns, heating radiators);
- demagnetization of old CRT TVs.
Thermistor
Thermistor (NTC thermistor) – a sensitive electronic component with a negative resistance coefficient. When heated, its internal resistance begins to drop. The component can serve as a temperature sensor or a variable resistor (as protection against overheating in electrical circuits). The thermistor parameters are not linear, which means that as the temperature rises, the resistance drops disproportionately and unevenly.
The thermistor body is made in the form of beads coated with ceramics or glass, which differ in size.
On the diagram it has the following designation:
One of the significant disadvantages of a thermistor is the discrepancy between the characteristics when manufactured using the same technical process. Components under the same conditions may produce different data, so when replacing one component with a similar one, recalibration is required. When used for a long time at elevated temperatures, NTC thermistors begin to degrade over time and need to be replaced.
The maximum operating temperature of the sensors is 300 degrees Celsius.
Scope of application of NTC thermistors:
- measuring the temperature of radio components of computers and mobile equipment (processors and memory chips, hard drives, video cards, etc.);
- in power supplies and lithium-ion (Li-ion) batteries as protection against overheating;
- in office equipment (laser printers and faxes);
- in 3D printers (for extruders and heated stages).
Essentially, both components are able to control temperature, but the resistance of the PTC thermistor tends to infinity as it heats up, while the resistance of the NTC thermistor tends to zero under the same conditions.To measure temperature, you need a controller that will calculate the resistance data of the components.
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