NTC Thermistor Power Limit Current Limit Resistor Surge Arrestor 8D20 8ohm 20mm Diameter

Thermistor-A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiter, temperature sensors (NTC type typically), self-resetting overcurrent protectors, and self-regulating heating elements.

 Thermistor differ from resistance temperature detectors (RTDs) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges.

Thermistor can be classified into two types, depending on the classification of k. If k is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, or posistor. If k is negative, the resistance decreases with increasing  temperature, and the device is called a negative temperature coefficient (NTC) thermistor.

Resistors that are not thermistors are designed to have a k as close to 0 as possible, so that their resistance remains nearly constant over a wide temperature range.

PRODUCT:

 1.Dimension:

2. Material: 

Coating: Phenolic resin 

Lead wire: CP lead wire

Coating color: Black

3. Technical data:

A. Zero power resistance at 25 ℃ : 3+/-20%

NTC Thermistor General Performance

a. Resistance value at Rated Zero-power R25: The design resistance of the thermistor usually refers to the resistance value got at Zero-power at 25  ℃, which is usually indicated on the thermistor.

b.The zero-power resistance: The zero-power resistance of a thermistor RT at a specified temperature(T) is the DC resistance measured when the power dissipation is negligible.

c. B: is the beta, or material constant expressed in kelvins.

d. Temperature coefficient of resistance: The temperature coefficient of resistance or alpha of an NTC thermistor is defined as:

e. Dissipation factor: The dissipation factor is defined as the ratio of the change in power dissipation and the resultant change in the thermistor's body temperature.

f.Thermal time constant : The thermal time constant refers to the necessary for an unloaded thermistor to vary its temperature by 63.2% of the difference between its mean temperature and the ambient temperature.

g.Temperature characteristic: The relation between the zero-power resistance and the temperature of the NTC thermistor body.

h.Solderability: Both lead wires are immersed into 235+/-5 solder for 2+/-0.5s, check the appearance.

i. Terminal Durability of soldering: The lead wire is soaked in molten solder at 260+/-10 from the bottom to a point of 2-2.5mm for 5+/-0.5minutes.After the device is left at room temperature for 2 hours, the resistance is measured.