High Score Solicitation Questions about thermistor materials

As far as I know, the materials used are different, and ordinary working environments can't be made... It feels like two different things ...

Personally, I think there is something wrong with your question, what do you want to do? The material is not chosen randomly, you have to tell us to do this and that?

Heat-sensitive materials can generally be divided into three categories: semiconductors, metals and alloys, which are briefly described as follows.

Semiconductor thermistor materials.

Such materials include single crystal semiconductors, polycrystalline semiconductors, glass semiconductors, organic semiconductors, and metal oxides. They all have a very large temperature coefficient of resistance and a high resistance to the turtle, and the sensitivity of the sensors made from them is also quite high. According to the temperature coefficient of resistance, it can also be divided into negative resistance temperature coefficient materials and positive resistance temperature coefficient materials.

In a limited temperature range, the negative resistance temperature coefficient material A can reach -6*10-2, and the positive resistance temperature coefficient material A can reach more than -60*10-2. For example, barium acid ceramics are an ideal semiconductor material with positive resistance temperature coefficient. The above two materials are widely used in temperature measurement, temperature control, temperature compensation, switching circuits, overload protection and time delay, etc., such as making thermistor thermometers, thermistor switches and thermistor thermometers, thermistor switches and thermistor delay relay errors.

Due to the exponential relationship between resistance and fluidity, this kind of material has a narrow temperature measurement range and poor uniformity

Metallic thermistor material.

These materials are widely used as RTD temperature measurement, current limiters and automatic constant temperature heating elements. Such as platinum resistance thermometer, nickel resistance thermometer, copper resistance thermometer, etc. Among them, the platinum side temperature sensor shows obvious high precision and high stability in various media (including corrosive media).

However, due to the scarcity and high cost of platinum, their wide application is limited to a certain extent. Copper temperature sensors are less expensive, but long-term use in corrosive media can lead to significant changes in static characteristics and resistance values. Recently, it has been reported that copper temperature sensors can be used in the -60 180 temperature range in air media.

However, in order to measure the temperature in -60 180 for a long time and 250 for a short period of time, a large number of nickel temperature sensors are generally used abroad, and nickel is considered to be an ideal material because of their high sensitivity, satisfactory reproducibility and stability.

Alloy thermistor material.

Alloy thermistor materials are also known as thermistor alloys. This alloy has a high resistivity and is sensitive to changes in resistance, making it a good material for making temperature-sensitive sensors. The performance requirements of thermistor alloys as temperature sensitive sensors are as follows:

1) Sufficiently large resistivity; (2) Quite high temperature coefficient of resistance; (3) It has a linear expansion coefficient close to that of the experimental material; (4) small strain sensitivity coefficient; (5) When heating and cooling in the working temperature range, the resistance temperature curve should have good repeatability.

Solution: 1) When the ambient temperature is 10, the thermistor r t500 , i=, can be obtained from Ohm's law

u 1 ir 1

2) The maximum current that the ammeter allows to pass through is large.

The supply voltage U=6V, the maximum resistance in the circuit is: <

The maximum resistance of the sliding rheostat is r=200, and the minimum resistance of the thermistor is 1 small.

r total r=300 200 =100, when the resistance of the thermistor is 100, the maximum ambient temperature of its operation can be known from Figure B 50

It may cause the device to not work because the current is throttled.

At the moment of energizing, the resistance of R is very small, a large AC current flows through the degaussing coil, R is also heated immediately, the resistance increases, the current becomes smaller, when it is stable, the temperature of the degaussing resistance is high enough, the resistance value of R is also large enough, the current of the degaussing coil is very small, and the degaussing is over. At this time, the heating of the negative resistance of r maintains a high enough temperature of the degaussing resistance to ensure that the positive resistance value of r is large enough and the coil current is small enough.

There is no R negative is the degaussing resistance of the two feet, because to maintain the temperature of R positive to make it in a high resistance state, the current flowing through the degaussing coil can not be very small, otherwise the temperature is not enough, so that after the degaussing is stable, the current in the coil is slightly larger, which may affect the display effect, and it is rarely used now.

When working normally, the thermal resistance is always hot, and before it cools down, there is already a current flowing through it to maintain this temperature.

A rheostat whose resistance changes with temperature.