The thermistor can also be used as an electronic circuit component for meter line temperature compensation and temperature difference cold junction temperature compensation. The automatic gain control can be realized by the self-heating characteristics of the NTC thermistor, and the RC oscillator stabilization circuit, the delay circuit and the protection circuit are formed. When the self-heating temperature is much higher than the ambient temperature, the resistance value is also related to the heat dissipation condition of the environment. Therefore, in the flow meter, the flow meter, the gas analyzer, and the thermal conductivity analysis, the characteristics of the thermistor are often used to prepare a dedicated detecting element.
1 over the surface control
Place two negative temperature coefficient thermistors in the high and low liquid level safe positions of the container and apply a constant heating current. The surface temperature of the thermistor immersed in the liquid at the bottom is the same as the peripheral temperature, while the surface temperature of the thermistor exposed to the air is higher than the peripheral temperature. If the liquid surface submerges the high resistance, the surface overflow decreases and the resistance increases. The judgment circuit can use the resistance value to notify the alarm device in time, and the action circuit cuts off the liquid inlet pipe to protect the liquid surface. If the liquid level drops to a low level, the bottom thermistor is gradually exposed to the air. At this time, the surface temperature rises and the resistance value decreases. The judgment circuit can use the resistance value to notify the action circuit to open the liquid supply line.
2 Temperature measurement
The thermistor as a measuring temperature is generally simple in structure. Due to its large resistance, the contact resistance at the junction can be ignored and can be applied to long-distance telemetry processes thousands of kilometers away.
3 temperature compensation
The negative temperature characteristic can be used to compensate in some electronic devices. When the current and temperature increase due to overload, the resistance of the thermistor increases the reverse pull-down current to compensate and protect. At this point, it should be noted that the thermistor needs to be connected in series in the electronic circuit.
4 temperature drawing
In electromechanical protection and control, the critical point thermistor is often connected in series in the relay control loop. When a device is overloaded in the event of a sudden failure, the temperature is increased. If the critical point resistance value suddenly drops, the relay current will exceed the operating current rating and act to cut and protect.
5 Temperature protection
Thermistors play a key role in the functional management of some devices, such as wireless phones, notebook computers, and so on. If the charging resistance is large, the battery of these devices will be charged quickly. But there is also the danger of overheating. If the heat causes the temperature to exceed the Curie temperature of the battery, the damage to the battery cannot be recovered. However, if the charging voltage is too low, the battery charging time will be unbearable. Using a thermistor in the battery, you can detect the overheating resistance or the overheating of the battery to adjust the charging speed. As a result, the voltage at which the battery starts to be charged is relatively large, so that it can be quickly charged with a large charging voltage in a relatively short period of time. When the threshold voltage or the critical temperature is to be reached, the charging speed can be controlled to be lowered, and then the charging can be completed relatively smoothly.
6 Overheat protection
For example, the notebook computer is getting smaller and smaller, the motherboard is very sensitive to temperature, and the motherboard is very close to the heat supply resistor. The increasing CPU frequency not only increases the speed of the CPU, but also makes it work at a high temperature. In this case, the surface-encapsulated thermistor can be both fast-responding and overheated, and is relatively easy to use.
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