What is the effect of degaussing on thermistors?

The degaussing effect is achieved by thermistors and degaussing coils. The principle is that energy is applied each time the machine is turned on and gradually removed after normal operation, so that the electron beam is only affected by the deflection coil and is not affected by any external stray magnetic field.

Therefore, the automatic degaussing thermistor should have a large impulse current and a very low residual current, and have good impulse resistance and high withstand voltage strength. At present, the development trend of automatic degaussing thermistors is small size, low resistance value, low residual current, high impact resistance and high reliability. When the device is turned on, the thermistor is in a low-impedance state, and a large current is formed in the degaussing coil, and the magnetic field line is 350at, which can effectively eliminate the influence of stray magnetic field.

Then the thermistor enters a high-impedance state under the influence of a large current, the loop current automatically attenuates, the residual current is very small, approximately an open circuit, and the magnetic field lines are reduced to the following to reach the acceptable limit under normal operation. When purchasing thermistors, we should pay attention to regular manufacturers, and the thermistors produced by Zhixu JEC have national certifications and high quality!

The color TV degaussing resistor is a special thermistor. Its resistance value at room temperature is very small, which is its nominal value. It has a large positive temperature coefficient of resistance.

After it is connected in series with the degaussing coil on the AC power supply, because the resistance of the degaussing coil is also very small, the current when it is just energized is very large, and the power consumption on the degaussing resistance is very large, causing it to heat up, and with the increase of temperature, its resistance increases sharply, so the current decreases sharply. But if the power is on all the time, its temperature will not drop to normal temperature. Because after dropping to room temperature, the above process will be repeated.

So when its temperature rises to a certain level, it won't rise again because the current decreases. Finally, if it is maintained at a certain temperature, the current will be maintained at a certain value. However, the current at this time is much smaller than at the beginning, and it can be ignored.

Therefore, it acts as an automatic delay switch. At the beginning of the start-up, the current is very large, which is equivalent to the switch on, and then the current is gradually reduced to the equivalent of an open circuit.

Due to this property, it has been widely used in many places. For example, the starting circuit of a refrigerator is connected to the power supply in series with the starting coil, and it is equivalent to an open circuit after the start-up.

But it's practically impossible to open the way. After the open circuit, the temperature will drop, the resistance value will decrease, and the current will rise again. Therefore, there must be a certain amount of current to keep it hot. After shutting down, it has no current, and it will return to normal.

The main function of thermistors is to be sensitive to temperature, and different resistance values are exhibited at different temperatures.

Thermistors can also be used as electronic circuit components for temperature compensation in instrumentation circuits and cold junction temperature compensation for thermocouples. Taking advantage of the self-heating characteristics of the negative temperature coefficient thermistor, automatic gain control is realized, which constitutes the amplitude stabilization circuit of the RC oscillator. When the self-heating temperature is much higher than the ambient temperature, its resistance is also related to the ambient heat dissipation conditions.

Thermistors are often used to analyze flow meters, flow meters, and thermal conductivity to make special sensing elements.

Detect the temperature. Converts temperature into an electrical signal.

Compensate. The resistance changes with temperature are used to compensate for the changes of other components with temperature.

Thermistor is a type of sensitive element, the resistance value of the thermistor will change with the change of temperature, different from the general fixed resistance, belongs to a class of variable resistance, widely used in various electronic components. Unlike resistance thermometers, which use pure metal, the materials used in thermistors are usually ceramics or polymers. Positive temperature coefficient thermistors have a higher resistance value when the temperature is higher, and negative temperature coefficient thermistors have a lower resistance value at higher temperatures, and they both belong to semiconductor devices.

Thermistors typically achieve high accuracy over a limited temperature range, typically -90 to 130

It is used to control the start or stop of the circuit.

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.

Degaussing refers to the elimination of the magnetization of the display, and to understand degaussing, you must first know what magnetization is.

What is commonly referred to as a display is magnetized, and what we see is an irregular color spot on the screen.

Magnetization is caused by the explosion-proof protective steel belt on the outside of the picture tube being approached by the surrounding magnetic materials (such as magnets, non-magnetic shielded speakers, etc.); Even if there is no magnetic material around, the prolonged action of the Earth's magnetic field is enough to cause the protective steel strip to be magnetized, just as a steel needle after being touched by a magnet is magnetic. Once the steel strip is magnetized, it will affect the normal deflection of the electron beam when the picture tube is working, resulting in the distortion of the image. (Due to the different working principles and structures--- liquid crystal displays are not affected by magnetic fields because there is no deflection scanning electron beam and no steel belt).

In order to eliminate the effects of magnetization, in fact, every time the display is turned on, the degaussing circuit will automatically activate to eliminate possible magnetization. The degaussing circuit works by using an alternating magnetic field (obtained by 220V alternating current applied to the circuit of the degaussing coil in series with a thermistor) to eliminate the constant magnetic field that is magnetized.

Some people say: you can't degauss frequently, it will be harmful. In fact, the inability to use degaussing frequently is not due to the adverse effects of degaussing on the display (basically none!). , but there is no need for this! Only in cases where the magnetization cannot be completely eliminated by each automatic degaussing, it is necessary to increase the degaussing effect manually to enhance the degaussing effect.

Some articles mentions: "The degaussing coil has a charging process after degaussing, and if the interval between degaussing is too short and the coil cannot be fully charged, then the second degaussing has little effect." "In fact, after degaussing, there is not a charging process, but the thermistor connected by the degaussing coil needs time to cool down to reduce the resistance back to the initial value to ensure that the degaussing coil works normally again, so it is correct that the necessary time interval is required for two degaussing.