Due to a wide variety of electronic components, here we mainly talk about resistance, capacitance, crystal diode, voltage regulator diode, inductance, variable capacitance diode, crystal triode, field effect transistor amplifier and other identification methods. Hope the following content can help you.
1. The resistance
Resistance identification method is mainly parameter identification method, parameter identification method is divided into index method, color code method and number code method.
1. The standard method
The nominal resistance value and technical parameters are directly marked on the surface of the resistor with Arabic numbers and unit symbols. The unit ohm of resistance value is represented by "ω", "K ω ", "M ω "and "G ω", and the allowable deviation is directly represented by percentage or ⅰ (±5%); ⅱ (±10%); ⅲ (±20%) represents.
Color standard method
Two-digit significant color code method: ordinary resistors use four ribbons to represent the nominal resistance value and allowable deviation, among which the first three ribbons represent the resistance value, the fourth represents the deviation, the first and second ribbons represent the significant number, the third represents the multiplier (power of 10), and the fourth represents the allowable deviation.
Three-digit effective color code method: precision resistance is represented by five ribbons, in which the first four ribbons represent the resistance value, the fifth represents the deviation, the first, second and third ribbons represent the significant number, the fourth represents the multiplier (power of 10), and the fifth represents the allowable deviation.
Color ring resistance first color band determination method: deviation ring and other rings spacing is larger, the deviation ring is wider. The first ring is closer to the end. There is no gold or silver in the effective digital ring (if the first or second ring from one end has gold or silver, the other end is the first ring. Four - color ring resistance of the deviation ring is generally gold, silver, white). Deviation ring no orange, yellow (if an end ring is orange or yellow, it must be the first ring). Test reading: The resistance value of the finished resistor is not greater than 22M ω. If the test reading is greater than 22M ω, it indicates that the reading is reversed. Test: test can be carried out when the above cannot be identified, but only if the resistor is in good condition. It should be noted that some manufacturers do not strictly follow article 1, 2, 3 of production, the above article should be considered comprehensively.
Resistance background color meaning method: blue represents the metal film resistance; Gray usually represents oxide film resistance; Beige (earthy yellow) represents carbon film resistance; Brown represents solid resistance; Green usually represents wire wound resistance; White represents cement resistance; Red, brown plastic case, that is non-inductive resistor.
Color ring resistance and color ring inductor appearance difference method: color ring inductor background color is green, pointed at both ends, large in the middle, the reading is the same as the color ring resistance, but the unit is microhm (μH).
Color ring resistance (left) and color ring capacitance (right)3 numerical notation is represented by two, three, or four Arabic digits. For three-digit notation, the first two digits indicate the significant number of resistance values, and the third digit indicates the number of zeros following the significant number. When the resistance value is less than 10 ohms, it is usually expressed as ×R×, and R is regarded as the decimal point. The unit is ohms. Deviations are usually expressed by symbols: B (±0.1%), C (±0.25%), D (±0.5%), F (±1%), G (±2%), J (±5%), K (±10%), M (±20%), N (±30%).
2. The capacitance
The identification method of capacitance and resistance is basically the same, divided into direct code, color code and number code. The basic unit of capacitance is expressed in Farad (F), and other units are: millimeter (mF), micrometer (uF), nano method (nF), and skin method (pF).
1 Farad =103 mfa =106 microfa =109 nm =1012 picograms
Capacitors with large capacity have their capacity value indicated directly on the capacitor, such as 10uF/16V. A capacitor with a small capacity has a capacity value indicated by letters or numbers on the capacitor. Letter representation: 1M =1000uF1P2=1.2PF1n=1000PF Digital representation: Generally, the capacity is represented by three digits. The first two digits are significant digits, and the third digit is the multiplier. For example, 102, 10 x 102PF=1000PF224, and 22 x 104PF=0.22uF
Diode identification is very simple, small power diode N pole (negative pole), in the diode appearance mostly marked by a color circle. Some diodes also use diode special symbols to indicate P pole (positive pole) or N pole (negative pole), there are also signs for "P", "N" to determine the polarity of the diode.
The positive and negative poles of leds can be identified by the short pins, the long ones being positive and the short ones being negative.
4. Regulated diode
The regulator diode is commonly used in the circuit "ZD" plus numbers, such as: ZD5 represents the regulator tube number 5.
Principle of voltage stabilizer diode: voltage stabilizer diode is characterized by breakdown, the voltage at both ends of the basic unchanged. In this way, when the regulator is connected to the circuit, if the voltage of the power supply fluctuates, or other reasons cause voltage changes at each point in the circuit, the voltage at both ends of the load will basically remain unchanged.
Fault features: voltage regulator diode fault mainly in open circuit, short circuit and stable value instability. Among the three faults, the former one shows the increase of supply voltage; The latter two faults are characterized by low supply voltage to zero or unstable output.
Inductance is usually represented by "L" plus a number in a circuit. For example, L6 represents the inductance numbered 6.
Inductance coil is made by winding an insulated wire around an insulated skeleton a certain number of times.
Dc can pass through the coil, dc resistance is the resistance of the wire itself, the voltage drop is very small; When the AC signal through the coil, both ends of the coil will produce self-induced electromotive force, the direction of the self-induced electromotive force and the direction of the applied voltage is opposite, blocking the AC through, so the characteristics of inductance is dc resistance AC, the higher the frequency, the greater the coil impedance. Inductance and capacitance can form an oscillating circuit in a circuit.
Inductance generally has the direct standard method and the color standard method, the color standard method is similar to the resistance. For example, brown, black, gold, and gold represent 1uH (5% error) inductance. The basic unit of inductance is: hen (H). 1H=103mH=106uH
Varactance diode is a special diode specially designed according to the principle that the junction capacitance of the ordinary diode "PN junction "can change with the change of the applied reverse voltage. In cordless telephone, varactance diode is mainly used in the high frequency modulation circuit of mobile phone or landline, realizing the modulation of low frequency signal to high frequency signal and transmitting out.
In the working state, the diode modulation voltage is generally applied to the negative pole, so that the capacitance of the diode's internal junction varies with the change of the modulation voltage
Varactor diode failure, mainly manifested as leakage or poor performance:
When leakage occurs, the high frequency modulation circuit will not work or the modulation performance will deteriorate.
When the variogram performance deteriorates, the high frequency modulation circuit works stably, causing distortion after the high frequency modulation signal is sent to the other party and received by the other party.
In one of the above cases, the same type of varactor diode should be replaced.
Crystal triode is commonly used in the circuit "Q" plus numbers, such as: Q17 stands for the number of 17 triode.
Crystal triode (short for triode) is a special device with two PN junctions inside and amplification ability. It is divided into NPN type and PNP type two types, these two types of audions can complement each other from the working characteristics, the so-called OTL circuit is PNP type and NPN type pair use. Crystal triode is mainly used for amplification in the amplifier circuit, there are three kinds of connection in common circuits.
8. Field effect transistors
Fet is widely used in various electronic devices because of its high input impedance and low noise. In particular, the utility tube can be used as the input stage of the whole electronic equipment to achieve performance that is difficult to achieve by ordinary transistors.
Fets can be divided into junction type and insulated gate type, and their control principles are the same.
Comparison of MOSFEts and transistors:
Mosfets are voltage control elements, while transistors are current control elements. When only a small amount of current is allowed from the signal source, the effect tube should be used; And in the signal voltage is low, and allow to take more current from the source of the condition, should choose transistor.
Field-effect tube is the use of most carriers conductive, so called monopole device, and the transistor is that most carriers, also use minority carriers conductive. This is called a bipolar device.
The source and drain of some FETs can be used interchangeably, and the gate voltage can be positive or negative, which is more flexible than transistors.
Fets are widely used in large-scale integrated circuits because they can work under very low current and voltage conditions, and their manufacturing process can easily integrate many FETs into a silicon chip.