Function of resistors and resistors classification
* 来源: * 作者: admin * 发表时间: 2019-09-25 10:53:26 * 浏览: 64
Functions of resistors:
The blocking action of the object to the current through is called resistance, and the components made of this blocking action are called resistors for short.
Resistor is one of the most widely used circuit components, accounting for more than 30% of the total number of components in electronic equipment, and its quality is good
Failure has a great effect on the stability of circuit operation. In the circuit, the role of the resistor is mainly to stabilize and regulate the circuit
Current and voltage, i.e., rise and fall, partial voltage, current limiting, shunt, isolation, filtering (in conjunction with the capacitor), matching and signal amplitude
Degree of regulation, etc.
Symbol of a resistor in a circuit:
Resistors are the most basic and common electronic components in electronic circuits. Resistors are generally represented by characters such as "R", "RN", "RF" and "FS".
Classification of resistors:
There are many types of resistors, which can be divided into fixed resistors and fixed resistors according to their working characteristics and their role in the circuit
There are two main types of variable resistors. Fixed resistors with a fixed value are called fixed resistors, and fixed resistors include many types, mainly
There are carbon resistor, carbon film resistor, metal film resistor winding resistor, etc. The resistance value is connected with adjustable resistance within a certain range
Devices are called varistors or potentiometers. Varistors are generally adjustable at both ends, potentiometers are generally adjustable at three ends.
If divided by the appearance of the resistor, generally divided into cylindrical resistor, button resistor and SMT resistor.
According to the different materials, the resistors can be divided into wire wound resistors, membrane resistors, carbon resistors, etc.
Resistors can be classified as precision resistors, high-frequency resistors, high-voltage resistors, high-power resistors, thermistors, and fuse resistors, depending on the purpose.
According to the lead, resistors can be divided into axial lead resistors, lead-free resistors, etc.
(1) Carbon film resistor:
Carbon film resistor is the earliest and most widely used resistor. It is made of carbon deposited on a ceramic substrate, and different resistance values can be obtained by changing the thickness or length of the carbon film. In fact, it is characterized by high temperature resistance. When the ambient temperature rises, its resistance value changes very little compared with other resistors, and it has good high-frequency characteristics, high precision, and is often used in precision instruments and other high-grade equipment.
(2) Metal film resistor:
Metal film resistor is made by deposition of a layer of alloy powder on a ceramic substrate under vacuum conditions. Different resistance values can be obtained by changing the thickness or length of the metal film. Metal film resistor is characterized by high precision, good stability, noise and low temperature coefficient. However, the metal film resistance structure is not uniform, so its pulse load capacity is poor, and the cost is high.
Tip:
Distinguish carbon film resistor from metal film resistor: Metal film resistor has five rings (1%) in appearance. The color ring of the carbon film resistor is four rings (5%). Metal film resistors are usually blue, carbon film resistors are usually earthen yellow or other colors. In addition, you can also use a multimeter to measure the resistance value of the resistor, and then use the heated ferroelectric near the resistor. If the resistance value changes a lot, it is the carbon film resistance, and the small change is the metal film resistance.
(3) Metal oxide film resistor:
Metal oxide film resistor is made by spray deposition of metal salt solution of tin and antimony on ceramic skeleton at high temperature. Compared with metal film resistor, it has the advantages of oxidation resistance, acid resistance, high temperature resistance, but its resistance value is generally small, can only be used to make low resistance value resistance.
(4) Wound resistor:
Wound resistors are made of constantan wire wound around an insulating skeleton. It has many advantages, such as high temperature resistance, high precision and high power. But its frequency modulation characteristic is poor, this is mainly because its distribution inductance is large. It is widely used in low frequency precision instrument. Common winding resistors are cement resistors, insurance resistors, etc.
(5) Safety resistor:
A fuse resistor is also called a fuse resistor. It has dual functions and has the electrical characteristics of an ordinary resistor under normal circumstances. Once the voltage in the circuit increases, the current increases or a component is damaged, the fuse will be blown off within a specified period of time, thus achieving the purpose of protecting other components. The safety resistance in the circuit is generally green patch type, black resistance, gray straight plug type and PTC, etc. In a circuit, a safe resistor is represented by an "F", usually marked as "0", "000", or rated current.
(6) Photoresistor:
A photoresistor is a sensitive resistor whose electrical conductivity varies with the number of photons absorbed, that is, a photosensitive resistor. It is made by using the photoelectric effect of the semiconductor, and its resistance varies with the intensity of incoming light. Photoresistors are mainly used for various automatic control, photoelectric counting. Photoelectric tracking and automatic exposure of cameras, etc.
(7)NTC and PTC thermistors:
NTC thermistor is a thermistor with a negative temperature coefficient change. Its resistance decreases with the increase of temperature. It can be used to stabilize the working point of the circuit. PTC hot resistor is a heat sensitive element with a positive temperature coefficient change. Before reaching a certain temperature, the resistance value decreases slowly with the rise of temperature. When exceeding this temperature, the resistance value increases sharply. This particular temperature point is called the Curie point. The Curie point of a PTC thermistor can be changed by changing the proportion of the components in the material. They are widely used in home appliances, such as the degaussing resistor of the color TV set, the thermostat of the rice cooker and so on.
(8) Varistor
Voltage-sensitive resistors refer to voltage-sensitive resistors, which are semiconductor devices made of zinc oxide. Their resistance value is close to infinity under normal conditions. When the voltage at both ends reaches or exceeds its critical point, the internal resistance decreases sharply and cannot be recovered, which is called breakdown. Voltage-sensitive resistors are mainly used in the ac input end of electrical equipment, as overvoltage protection, when the input voltage is too high, its resistance value will be reduced, so that the safety tube connected in series in the input circuit fuses, cut off the input, thus protecting electrical equipment.
(9) other sensitive resistors
In practical applications, other sensitive resistors commonly used are humidity - sensitive resistors, magnetic - sensitive resistors, gas - sensitive resistors and force - sensitive resistors.
(10) Exhaust resistor:
An expeller is a type of combined resistor, also known as a lumped resistor, that integrates discrete resistors arranged in a regular pattern. It is a network of resistors that is small in size. Structured, high precision, suitable for electronic equipment and computer circuits. Row resistors are usually represented by RN. The main board of the discharge resistor has 8 and 10 pin two kinds, of which 8 pin is used more. In main board, the general use of "472", "330", "220" row resistor, such as the "330" said resistance to 33 Ω.
(11) Variable resistor:
A variable resistor is generally a potentiometer. A potentiometer is a resistor whose resistance can be continuously adjusted. Varistors generally have three pins, including two fixed pins and a moving pin; An adjusting port is provided through which the moving plate can be changed to change the resistance value of the resistor. Varistors are commonly used in recorders, televisions, and other devices. To control the tone, the volume. Adjust brightness, contrast, etc.
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