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# Resistor-General Knowledge Analysis

1.1 The meaning of a resistor: The part of a circuit that impedes current and causes energy consumption is called a resistor.

1.2 Abbreviations for 1.2 Resistors: R (Resistor) and Removal RN

1.3 Resistors in Circuit Symbols: R or WWW

1.4 Common units of 1.4 resistors: kiloohms (K_), megaohms (M_)

1.5 Unit Conversion of 1.5 Resistors: 1 Mega Ohm = 103 KOhm = 106 Ohm

1.6 The characteristic of resistor: The resistance is linear, that is, the voltage at both ends of the resistor is proportional to the current flowing through the resistor, and the current intensity through the conductor is inversely proportional to the resistance of the conductor. That is Ohm’s Law: I = U/R.

1.7 resistors are used for shunting, current limiting, voltage dividing, bias, filtering (combined with capacitors) and impedance matching.

1.8 resistors are represented by “R” plus numbers in the circuit. For example, R15 represents a resistor numbered 15.

1.9 There are three kinds of parameter labeling methods for resistors in circuits, namely, direct labeling method, color labeling method and number labeling method.

• A. The direct marking method is to mark the nominal value of the resistor directly on the resistor body with numbers and characters, and its allowable deviation is expressed by percentage. The unsigned deviation value is +20%.
• B. Digital labeling is mainly used for small-volume circuits such as patches. In three digits, the first from left to right, the second digit represents the effective number, the third digit represents the power of 10 or R represents 0. For example, 472 represents 47102_ (i.e. 4.7 K); 104 represents 100 K; and R22 represents 0.22_, 122 = 1200_ = 1.2 K, 1402 = 14000_. = 14K_, R22 = 0.22, 50C = 324100 = 32.4K_, 17R8 = 17.8, 000 = 0, 0 = 0.
• C. The color ring labeling method is the most widely used. Ordinary color ring resistors are represented by four rings. Precision resistors are represented by five rings. The color ring near one end of the resistor body is the first ring, while the other end with more color of the resistor body is the last ring. For example, if the color ring resistor is represented by four rings, the first two digits are valid and the third digits are valid. The fourth ring is the error range of the color ring resistor. ( If the color ring resistor is represented by five rings, the first three digits are valid numbers, and the fourth digit is 10 times the power. The fifth ring is the error range of the color ring resistor. )
• D. SMT precision resistance is usually expressed by three-bit mark. Generally, two digits and one letter are two valid digits. The letters represent 10 times the power. However, it is necessary to search in the precision resistance inquiry table according to the actual situation. The following is the precision resistance inquiry table.A. The direct marking method is to mark the nominal value of the resistor directly on the resistor body with numbers and characters, and its allowable deviation is expressed by percentage. The unsigned deviation value is +20%.
• B. Digital labeling is mainly used for small-volume circuits such as patches. In three digits, the first from left to right, the second digit represents the effective number, the third digit represents the power of 10 or R represents 0. For example, 472 represents 47102_ (i.e. 4.7 K); 104 represents 100 K; and R22 represents 0.22_, 122 = 1200_ = 1.2 K, 1402 = 14000_. = 14K_, R22 = 0.22, 50C = 324100 = 32.4K_, 17R8 = 17.8, 000 = 0, 0 = 0.
• C. The color ring labeling method is the most widely used. Ordinary color ring resistors are represented by four rings. Precision resistors are represented by five rings. The color ring near one end of the resistor body is the first ring, while the other end with more color of the resistor body is the last ring. For example, if the color ring resistor is represented by four rings, the first two digits are valid and the third digits are valid. The fourth ring is the error range of the color ring resistor. ( If the color ring resistor is represented by five rings, the first three digits are valid numbers, and the fourth digit is 10 times the power. The fifth ring is the error range of the color ring resistor. )

1.10 The size of SMT resistance is expressed as length and width (e.g. 0201, 0603, 0805, 1206, etc.), and specifically 02 as length is 0.02 inches and width is 0.01 inches).

1.11 In general, there are two ways of connecting resistors in circuits: series connection method and parallel connection method.

1.12 The calculation method of series-parallel connection of more than resistors:

• Series: R total string = R1 + R2 + R3 + Rn.
• Parallel connection: 1/R aggregate = 1/R+2/R+3/R_1/Rn

1.13 Testing of Resistors:

• A. Determine the resistance by pointer multimeter: first choose the measuring gear, then put the multiplier knob in the proper gear. Generally, resistors below 100 ohms can choose RX1, resistors below 100 ohms can choose RX10, resistors between 1K ohm and 10K ohm can choose RX100, resistors between 10K and 100K ohms can choose RX1K and above 100K ohms. The resistor can be RX10K.
• B. After the selection of measuring gear is determined, the resistance of the multimeter is calibrated to 0. The method of calibrating 0 is to connect the metal rods of the two pens of the multimeter and observe the position of the pointer to 0. If it is not in the position of 0, adjust the zero knob pointing to the zero position of the resistance scale.
• C. Next, the two pens of the multimeter are connected with the two ends of the resistor respectively. The needle should refer to the corresponding resistance scale. If the needle is fixed and the indication is unstable or the indication value differs greatly from the indication value on the resistor, it indicates that the resistor has been damaged.
• D. Use digital multimeter to judge the resistance. Firstly, adjust the gear knob of the multimeter to the appropriate gear of the ohm gear. Generally, resistors below 200 ohms can choose 200, 200-2K ohm resistors can choose 2K, 2K-20K ohms can choose 20K, 20K-200K ohm resistors can choose 200K, 200K-200M ohm resistors can choose 2M ohm.2M-20K. The resistor of M ohm is 20M, and the resistor above 20M ohm is 200M.