Electronics - Voltage and Current - Discussion

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 limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.

Rheostat-Current controling device with resistance coil
Potentiometer-Votage varing and measuring circuit
Photoconductive cell- Produces current when light incident on it

All the above have less temperature coefficents.

Thermistors differ from resistance temperature detectors (RTD) 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, while thermistors typically achieve a higher precision within a limited temperature range, typically −90 °C to 130 °C.

It is well known that resistance of metallic conductors increases with temperature, while that of semiconductors generally decreases with temperature. Resistance thermometers employing metallic conductors for temperature measurement are called Resistance Temperature Detector (RTD) , and those employing semiconductors are termed as Thermistors.

The NTC thermistors is more common. Essentially, they are made from oxides of iron, manganese, magnesium etc.

The Positive Temperature Coefficient (PTC) thermistor have limited use and they are particularly used for protection of motor and transformer widings.

They have low and relatively constant resistance below a threshold temperature TR, beyond which the resistance increases rapidly. The PTC thermistors are made from compound of barium, lead and strontium titanate.

Assuming, as a first-order approximation, that the relationship between resistance and temperature is linear, then:

(Δ R)=k(Δ T),

where

ΔR = change in resistance
ΔT = change in temperature
k = first-order temperature coefficient of resistance

Thermistors can be classified into two types, depending on the sign 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.

Thermistor is a type of resistor whose resistance is dependent on 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. Thermistors are of two opposite fundamental types:.

With NTC, resistance decreases as temperature rises to protect against inrush overvoltage conditions. Commonly installed in parallel as a current sink.

With PTC, resistance increases as temperature rises to protect against overcurrent conditions. Commonly installed in series as a resettable fuse.

ANSWER - Thermistor is right.

Yes, right @Yogesh & Ravikumar.

They asked only which is temperature based resistor, NTC and PTC both are temperature based thermistor resistors it may be an NTC or PTC.

Thermistors are two opposite fundamental types:

1) NTC- Negative Temperature Coefficient. If here temperature increases resistance decreases.

2) PTC- Positive Temperature Coefficient. If here temperature increases resistance also increases.

Thermistors are special solid temperature sensors that behave like temperature-sensitive electrical resistors. No surprise then that their name is a contraction of "thermal" and "resistor". There are basically two broad types, NTC-Negative Temperature Coefficient, used mostly in temperature sensing and PTC-Positive Temperature Coefficient, used mostly in electric current control.

Thermistor has two type.
PTC Thermistor "POSISTOR" (for heaters, motor starters, over current protection, over heat sensing & automotive).
NTC thermistor (for inrush current suppression, temperature sensor / compensation & automotive) are offered.
Thermistor is a temperature measuring device.

NTC thermistors decrease in resistance as the temperature increases. PTC thermistors are Positive Temperature Coefficient resistors generally made of polycrystalline ceramic materials that have a high positive temperature coefficient, which increases in resistance as the temperature increases.

Note that the question is which one is designed to be sensitive to temperature. And it is thermistor. i.e. , it is designed with the motto to be temperature Sensitive.

However the others may have the sensitivity with temp in practical cases. But they not intendedly designed to be sensitive.

Thermistor is a kind of resistor depends upon the coefficient it provides resistance.

1. PTC- if temperature is increased resistance also increases.

2. NTC- if temperature is increased resistance also decreases.