Thermistor

The thermistor is a sensitive element of a class (Metal Oxide Varistor), in accordance with the different temperature coefficient divided by a positive temperature coefficient thermistor (PTC) and the negative temperature coefficient thermistor device (NTC). The typical characteristics of the thermistor is sensitive to temperature, and exhibit a different resistance value in the different temperatures. The positive temperature coefficient thermistor (PTC) when the higher the temperature the greater the resistance value of the negative temperature coefficient thermistor (NTC) resistance value is lower at higher temperatures, and they belong to the same semiconductor device.

Detected with a multimeter, Ohm range (depending on the nominal resistance value determined stalls generally R × 1 block), specific operation in two steps: First, the room temperature detection (indoor temperature close to 25 ° C) with alligator clips instead of table pen clip live two pin PTC thermistor measured the actual resistance, compared with nominal resistance, a difference that is within ± 2Ω normal. Actual resistance with nominal resistance difference is too large, its performance is bad or corrupted. Secondly warmed detection can be carried out on the basis of normal room temperature test, the second test - warmed detected, a heat source (for example, electric iron) close to the thermistor heating observed Wildcard represents a number, this time as see The Wildcard shown with increasing temperature change, which indicates that the resistance value is gradually changed (negative temperature coefficient thermistor NTC resistance value becomes small, positive temperature coefficient thermistor PTC resistance becomes large) when resistance to change to a certain value, the data will be gradually stabilized, the thermistor is normal, if the resistance did not change, their performance deteriorates, you can not continue to use.

Testing should pay attention to the following points: (1) Rt is the manufacturers measured at an ambient temperature of 25 ° C, measured with a multimeter Rt should the ambient temperature close to 25 ℃, to ensure that the test can be reliability. (2) measurement of power shall not exceed the specified value, in order to avoid the current thermal effects caused by measurement error. (3) Note operating correctly. Test, do not hand pinch the thermistor body to prevent the impact of the body temperature of the test. (4) Be careful not to be too close or direct contact with the thermistor heat source with PTC thermistor to prevent scorch.

Thermistor(Metal Oxide Varistor)

Using the principle of the temperature induced resistance change. If the concentration of electrons and holes respectively, n, p, migration rates were μN, μP, the conductance of the semiconductor is:

σ = q (nμn + pμp)

N, p, μn, μp are dependent on the temperature T of the function, the conductance is a function of temperature, by measuring conductance deduce the temperature level, and can make the resistance - temperature characteristics curve. This is the working principle of the semiconductor thermistor.

Thermistor, including a positive temperature coefficient (PTC) and a negative temperature coefficient (NTC) thermistor, and the critical temperature of the thermal resistor (CTR).

Thermistor is characterized by: (1) high sensitivity, temperature coefficient of resistance than metal 10 to 100 times higher than 10-6 ℃ temperature changes can be detected; ② Operating temperature range is wide, room temperature device is suitable for -55 ℃ ~ 315 ℃, high temperature devices applicable temperature higher than 315 ℃ (currently a maximum up to 2000 ° C), low-temperature devices applicable to -273 ℃ to 55 ℃; ③ small size, capable of measuring the gap can not be measured by other thermometer cavity and biological the temperature of the blood vessels; ④ easy to use, the resistance value can be between 0.1 ~ 100kΩ arbitrarily selected; ⑤ easy processing into complex shapes, can be mass; ⑥ The stability is good, strong overload.(Metal Oxide Varistor)