Basic knowledge of electronic components (1) - resistance
The resistance of the conductive body to the current is called resistance, with the symbol R, the unit is Ohm, ohm, ohm, respectively, using K,, M.
First, the resistance of the model name method:
The domestic made resistor type is composed of four parts (not applicable to sensitive resistance).
The first part: the main said, with the letter, said the name of the product. Such as R, W, said the resistance potentiometer.
The second part: materials, represented by the letter said, what material is composed of a resistor body, T- carbon film, H- film, S- organic carbon, inorganic solid, solid N- J- metal film, Y- film, C- film, nitride I- glass glaze film and X- wire.
The third part: classification, the general use of digital representation, the individual type with letters, said that the product belongs to what type. 1- ordinary, 2- ordinary, 3- ultra high frequency, 4- high resistance, high temperature 5-, 6- precision, 7- precision, 8- high voltage, 9- special, G- high power, T- adjustable.
The fourth part: serial number, expressed by the number of similar products in different varieties, in order to distinguish the product‘s appearance size and performance indicators, such as: T R 11 type common carbon film resistors
Two, the classification of resistors
1, wire wound resistor: universal wire wound resistor, precision wire wound resistor, high power wire wound resistor, high frequency wire wound resistor.
2, thin film resistors: carbon film resistors, carbon film resistors, metal film resistors, metal oxide film resistors, chemical deposition film resistors, glass glaze film resistors, metal nitride film resistors.
3, solid solid carbon resistor resistor: the synthesis of inorganic and organic synthesis of solid carbon resistor.
4, sensitive resistor: pressure sensitive resistor, thermistor, photosensitive resistor, force sensitive resistor, gas sensitive resistor, humidity sensitive resistor.
Three, the main characteristic parameters
1, the nominal resistance resistor: marked above the resistance.
2, the allowable error difference: nominal resistance and actual resistance to nominal resistance than the known resistance percentage deviation, it represents the precision resistor. Allowable error and accuracy level of the corresponding relations are as follows: + 0.5%-0.05, + 1%-0.1 (or 00), + 2%-0.2 (or 0), + 5%- grade I, + 10%- II, + 20%- III
3, rated power: 90-106.6KPa at atmospheric pressure and ambient temperature for normal 55 DEG C 70 conditions, the maximum power dissipation of the resistor allows long-term work.
Wire wound resistors rated power series (W): 1/20, 1/8, 1/4, 1/2, 1, 2, 4, 10, 16, 25, 40, 50, 75, 100, 150, 250, 500
Non wire wound resistors rated power series (W): 1/20, 1/8, 1/4, 1/2, 1, 2, 5, 10, 25, 50, 100,,,,,,, and
4, rated voltage: rated power conversion and voltage resistance by the.
5, maximum operating voltage: maximum allowable working voltage. When working at low pressure, the maximum operating voltage is low.
6, temperature coefficient: the relative change of the resistance value caused by temperature change 1. The smaller the temperature coefficient, the better the stability of the resistance. The resistance increases with the temperature of the positive temperature coefficient, and negative temperature coefficient.
7, the aging coefficient: rated power load resistor in the long term, the percentage of relative change of resistance, it is a parameter that indicates the lifespan of the resistor.
8, the voltage factor: in the specified voltage range, the voltage of 1 volts per change, the relative change of the resistor.
9, noise: voltage fluctuation of an irregular in the resistor, consists of two parts: thermal noise and current noise, thermal noise is due to free electrons inside the conductor irregular, changes in the voltage conductor of arbitrary two irregular.
Four, the resistance value of a resistor marking method
1, standard method to mark resistance in the resistor surface with the number and the unit symbol, which allows the direct use of error percentage, if the resistance does not note the deviation, are + 20%.
2, text symbols: both Arabia and digital symbols regular combinations to represent the nominal resistance, the allowable deviation with text symbols. Sign in front of the digital representation of integer resistance, the number after the decimal value and in turn represent the first second decimal value.
Text symbols that indicate the allowable error
Text symbol F G J K M D
Allowable deviation + 0.5% + 1% + 2% + 5% + 10% + 20%
3, digital method: in the resistor with three digit representation of the nominal value of the mark method. Digital from the left to the right, the first, two for the effective value, third for the index, that is, the number of zero units for europe. Deviation is usually represented by character symbols.
4, color: with different colors or mark the nominal resistance and allowable deviation in the resistor surface. Most of the foreign resistance color method.
Black -0, brown -1, red -2, orange -3, yellow -4, green -5, blue -6, purple -7, gray -8, white -9, gold - 5%, silver - 10%, colorless - 20%
When the resistance is the city of Victoria, the last ring will for gold or silver, two to third for a valid number, the number fourth, as the deviation.
When the resistance of the five rings, the last ring and the greater distance from the front of the city. The top three for effective figures, fourth for the number fifth, for the deviation.
Five, commonly used resistors
Potentiometer is a kind of mechanical and electrical components, by the brush on the resistance of the slide, and the brush to achieve a certain relationship between the output voltage.
1.1 synthetic carbon film potentiometer
The resistor is used after grinding of carbon black, graphite, quartz and other materials to be coated on the surface of the matrix, the process is simple, is currently the most widely used. Is characterized by high resolution and good abrasion resistance, long service life. The disadvantage is the current noise, nonlinear, moisture resistance and resistance stability.
1.2 organic solid potentiometer
The organic solid potentiometer is a new type of potentiometer, which is used to press the organic electric resistance powder into the groove of the insulator. Compared with the carbon film potentiometer, the organic solid potentiometer has the advantages of good heat resistance, high power, high reliability and good wear resistance. But the temperature coefficient, high noise, poor resistance, tide complicated manufacturing process, poor precision resistance. In the miniaturization, high reliability, high wear resistance of electronic equipment and the AC, DC circuit used for regulating voltage, current.
1.3 metallic glass uranium potentiometer
In accordance with a certain pattern, the metallic glass uranium resistance paste is coated on the ceramic substrate by the screen printing method, and the material is sintered at high temperature. Features are: wide range of resistance, good heat resistance, strong overload capacity, moisture resistance, wear resistance are very good, is very promising varieties of potentiometer, disadvantages of contact resistance and current noise.
1.4 wire wound potentiometer
Wire wound potentiometer is Kang copper wire or nichrome wire as a resistor, and put it in the wound into the insulated skeleton. Wire wound potentiometer is characterized by small contact resistance, high precision, low temperature coefficient, the disadvantage is the low resolution, low resistance, high frequency characteristics. Mainly used as a divider, rheostat, instrument zero point and etc..
1.5 metal film potentiometer
The resistance body of the metal film potentiometer can be composed of alloy film, metal oxide film, metal foil, etc.. Is characterized by high resolution, high temperature, low temperature coefficient, low noise, good smoothness.
1.6 conductive plastic potentiometer
With the special process of DAP (adjacent benzene two formic acid two dilute propyl) coated on the insulating body resistance paste, heating polymerization into a resistive film or solid powder DAP resistance thermoplastic pressure groove formed in the insulating base within the body as resistance. Features: smooth and good resolution, excellent wear resistance and long service life, low noise, high reliability, resistance to chemical corrosion. Servo system for universal devices, missiles, aircraft radar antennas, etc..
1.7 potentiometer with switch
Rotary switch potentiometer, push pull switch potentiometer, push switch potentiometer
1.8 preset potentiometer
Pre adjustable potentiometer in the circuit, when debugging, adjust the position with wax seal, no regulation in general.
1.9 straight slide type potentiometer
The resistance value is changed by the direct sliding mode.
1.10 double potentiometer
There are different axis dual potentiometer and coaxial dual potentiometer
1.11 contactless potentiometer
Non contact potentiometer to eliminate the mechanical contact, long life, high reliability, sub photoelectric potentiometer, magnetic sensitive potentiometer, etc..
2, solid carbon resistor
With strong resistor carbonaceous particles conductive material, filler and binder made of an entity. Features: low price, but the resistance error, noise voltage, poor stability, the less.
3, wire wound resistor
A high resistance alloy wire is wound on the insulating frame, and the outer coating is coated with a heat insulating layer or an insulating varnish. Wirewound resistor has a low temperature coefficient, high precision resistance, good stability, heat resistance, corrosion resistance, mainly high power precision, disadvantage is the high frequency performance is poor, the large time constant.
4, thin film resistor
The evaporation method is used to make a certain electrical resistivity material to be deposited on the surface of the insulating material. Mainly as follows:
4.1 carbon film resistor
The crystalline carbon is deposited on the ceramic bar framework. Carbon film resistor of low cost, stable performance, wide range of resistance, temperature coefficient and voltage coefficient is low, is currently the most widely used.
4.2 metal film resistor.
Vapor deposited on the surface of ceramic rod framework by vacuum evaporation method. Metal film resistance than the carbon film resistance of high precision, good stability, noise, small temperature coefficient. In the instrument and meter and communication equipment in a large number of.
4.3 metal oxide film resistor
Depositing a layer of metal oxide on an insulating rod. Because of its itself is oxide, so high temperature stability, heat shock, strong load capacity.
4.4 synthetic membrane resistance
The conductive composite suspension is coated on the substrate, so that the resistance of the film is also called. Because of the granular structure of the conductive layer, the noise is big, the precision is low, mainly used for the production of high voltage, high resistance and small resistor.
5, metal glass uranium resistor
The metal powder and the glass uranium powder are mixed, and the screen printing method is used on the substrate. Resistance to moisture, high temperature, low temperature coefficient, mainly used in thick film circuit.
6, patch resistance SMT
Sheet resistance is a form of uranium resistance of metallic glass, and its resistance is high reliability ruthenium series glass uranium material is sintered at high temperature. Small size, high accuracy, good stability, because it is a piece of the top piece, so the high frequency performance.
7, sensitive resistance
Sensitive resistance refers to the device characteristics of temperature, voltage, humidity, light, gas, magnetic field, pressure, such as the role of sensitive resistors. The symbol is a sensitive resistance in common resistance slash symbol, and other type of annotation, sensitive resistance such as: T. v.
7.1, pressure sensitive resistance
There are mainly silicon carbide and Zinc Oxide pressure sensitive resistance, Zinc Oxide has more excellent characteristics.
7.2, humidity sensitive resistance
The humidity sensitive resistance mainly comprises a humidity sensitive resistor, a humidity sensitive resistor, a humidity sensitive resistor, and a humidity sensitive resistor. The humidity resistance of the lithium chloride humidity resistance decreases with the increase of humidity, the disadvantage is that the test scope is small, the characteristic is not good, and the temperature is affected by the temperature. For the shortcomings of low temperature carbon humidity resistance and low sensitivity, resistance is affected by temperature, the aging characteristics, use less. Oxide humidity resistance superior performance, can be used for a long time, the influence of temperature is small, there is a linear relationship between the resistance and humidity change. A tin oxide, nickel ferrite materials, etc..
7.3, photosensitive resistance
The photosensitive resistance is the electronic components with the light conductivity changes, when some substances are light, the carrier concentration increases and increases the conductivity, this is the photoconductive effect.
7.4, gas sensitive resistance
A gas absorption using some semiconductor after oxidation reduction reaction is made, the main component is metal oxide, the main varieties are: metal oxide gas sensing resistance, composite oxide gas sensitive resistors, ceramic gas sensing resistance.
7.5, force sensitive resistance
Is a force sensitive resistor resistance value varies with the change of pressure, foreign called piezo resistor. The so-called stress resistance effect is that the resistivity of the semiconductor material changes with the change of the mechanical stress. Can be made of a variety of torque meters, semiconductor microphones, pressure sensors, etc.. The main varieties are silicon force sensitive resistor, selenium and te alloy force sensitive resistor, relatively speaking, the alloy resistor has higher sensitivity.
7.6, thermal resistance
The thermistor is a kind of sensitive element, and its resistance value will change with the temperature of the temperature of the thermistor body, and it has the characteristics of the semiconductor.
According to the different temperature coefficient of thermal resistance is divided into:
Positive temperature coefficient thermistor (PTC thermistor)
Negative temperature coefficient thermistor (NTC thermistor)
Positive temperature thermistor (Thermistor PTC)
PTC is the abbreviation of Coefficient Positive Temperature, positive temperature coefficient, temperature coefficient of the pan semiconductor material or device. Usually we mentioned is PTC. Temperature coefficient thermistor thermistor, referred to as PTC.
PTC thermal resistance is a typical semiconductor resistance temperature sensitivity, more than a certain temperature (Curie temperature), the resistance value of the temperature increases with the increase of the temperature.
PTC thermistor is divided into different materials according to their different materials:
Ceramic PTC thermistor
Organic polymer PTC thermistor
At present a large number of PTC thermistor types are used:
PTC thermistor for constant temperature heating
PTC thermistor for over current protection
PTC thermistor for air heating
PTC thermistor for delay start
PTC thermistor for sensor
Using PTC automatic degaussing thermistor
In general, organic polymer PTC thermistor is suitable for over current protection, ceramic PTC thermistor can be applied to all kinds of purposes listed above.
Negative temperature thermistor (Thermistor NTC)
NTC is the abbreviation of Coefficient Negative Temperature, mean negative temperature coefficient, negative temperature coefficient refers to large semiconductor materials or components. Usually we mentioned NTC refers to the negative temperature coefficient thermistor thermistor, referred to as NTC.
NTC thermistor is a typical semiconductor resistance with temperature sensitivity, and its resistance value increases with the increase of temperature.
The NTC thermistor is based on manganese, cobalt, nickel and copper oxide as the main material, the ceramic manufacturing process. These metal oxide materials have semiconductor properties, because the way completely similar to the conductive germanium, silicon and other semiconductor materials. When the temperature is low, the oxygen carrier material (electronic and a small number of cavities), so its resistance value is higher; with the increase of temperature, the number of carrier increases, so the resistance value decreased.
NTC thermistor is divided according to its purpose:
Power type NTC thermistor
Compensation type NTC thermistor
Temperature measurement type NTC thermistor
Temperature sensor NTC thermistor