The resistance in the circuit is represented by "R" plus a number. For example, R 1 indicates that the main functions of the resistor numbered 1 in the circuit are shunt, current limiting, voltage division, bias, etc. 1, parameter identification: the unit of resistance is ohm (ω), and the amplification unit is kiloohm (kω) and megaohm (m).

The conversion method is: 1 megohm = 1000 kiloohm = 1000000 ohm. There are three methods to mark the parameters of resistors, namely, direct marking, color marking and digital marking. A, digital marking method is mainly used for small-volume circuits such as patches, for example, 472 means 47×100Ω (i.e. 104 means 100Kb), and color ring marking method is adopted at most. Here are some examples: four-color ring resistor Five-color ring resistor (precision resistor)

2. The relationship between color code position and resistance rate is shown in the following table: allowable deviation of color effective digital rate (%) silver /x0.0 1 10 gold /x0. 1 5 black 0 +0/ brown1x10/kloc.

Second, the capacitance.

1, the capacitance is generally represented by "c" plus a number in the circuit (for example, C 13 is represented by the number 13). The capacitor of this element consists of two metal films, which are adjacent to each other and separated by insulating materials. The characteristic of capacitance is that the capacitance of alternating current can store electric energy, and the blocking effect of capacitance on alternating current signal is called capacitive reactance. It is related to the frequency and capacitance of AC signal. Capacitance XC= 1/2πf c (f stands for the frequency of AC signal and c stands for capacitance). There are electrolytic capacitors, ceramic capacitors, patch capacitors, monolithic capacitors, tantalum capacitors and polyester capacitors commonly used in telephones.

2. Identification method:

The identification method of capacitance is basically the same as that of resistance, and the basic units of the three capacitors are all expressed by La (f). Other units include: mF, uF, nF and pF, where: 1 Farah =103mf =106mf =109nf =106544. For example, 10 uF/ 16V, and the capacitance value of a small capacitor is expressed by letters or numbers. Letter representation:1m =1000uf1p 2 =1.2pf1n =1000pf digital representation. The third digit is the magnification, such as: 102 means10×102pf =1000pf224 means 22× 104PF=0.22 uF3, and the capacitance error indicator number F G J K L M allows error/klm.

Third, crystal diode.

Crystal diodes are usually represented by "D" plus numbers in circuits. For example, D5 is represented by the number 5.

Identification method:

The identification of diodes is very simple. The N pole (negative pole) of most small power diodes is marked with a colored circle. Some diodes also use diode-specific symbols to represent the P pole (positive pole) or the N pole (negative pole), and some light-emitting diodes with symbols marked as "P" and "N" to determine the diode polarity can be identified by the length of the pin, with long legs as the positive pole and short legs as the negative pole. 3. Precautions for testing. The red contact pin is connected to the anode of the diode and the black contact pin is connected to the cathode of the diode. At this point, the measured resistance is the forward on resistance of the diode. This is the opposite of pointer multimeter's pen and watch connection. The commonly used 1N4000 series diodes are compared as follows: model1n4001n40021n40031n40041n40051n4005.