resistance"
The resistance of a conductor to current is called resistance, which is represented by the symbol R, and the units are ohm, kiloohm, and megohm, which are expressed by Ω, kΩ, and MΩ, respectively.
First, the model name of the resistor
The domestic resistor model is composed of four parts (not applicable to sensitive resistors)
The first part: the main title, which is represented by a letter, indicating the name of the product. For example, R means resistance and W means potentiometer.
Part II: Materials, which are represented by letters, indicate what material the resistor body is made of, T-carbon film, H-synthetic carbon film, S-organic solid, N-inorganic solid, J-metal film, Y-nitride film C-deposited film, I-glass glaze film, X-wire winding.
The third part: classification, generally expressed by numbers, individual types are represented by letters, indicating what type the product belongs to. 1-Ordinary, 2-Ordinary, 3-UHF, 4-High Resistance, 5-High Temperature, 6-Precision, 7-Precision, 8-High Voltage, 9-Special, G-High Power, T-Adjustable.
The fourth part: serial number, expressed by numbers, which indicates different varieties of the same kind of products, in order to distinguish the appearance size and performance indicators of the products. Example: R T 1 1 ordinary carbon film resistor a1}
Classification of resistors
1. Wirewound resistors: General-purpose wirewound resistors, precision wirewound resistors, high-power wirewound resistors, and high-frequency wirewound resistors.
2. Thin film resistors: carbon film resistors, synthetic carbon film resistors, metal film resistors, metal oxide film resistors, chemical deposition film resistors, glass glaze film resistors, metal nitride film resistors.
3, solid resistors: inorganic synthetic solid carbonaceous resistors, organic synthetic solid carbonaceous resistors.
4. Sensitive resistors: varistor, thermistor, photoresistor, force-sensitive resistor, gas-sensitive resistor, and humidity-sensitive resistor.
Third, the main characteristic parameters
1. Nominal resistance: The resistance marked on the resistor.
2. Allowable error: The percentage of the difference between the nominal resistance value and the actual resistance value and the nominal resistance value is the resistance deviation, which indicates the accuracy of the resistor.
The corresponding relationship between the allowable error and accuracy level is as follows: ± 0.5% -0.05, ± 1% -0.1 (or 00), ± 2% -0.2 (or 0), ± 5% -Ⅰ level, ± 10% -Ⅱ level, 20% -Ⅲ grade
3. Rated power: Under normal atmospheric pressure of 90-106.6KPa and ambient temperature of -55 ℃ ～ + 70 ℃, the maximum power that the resistor can dissipate in long-term operation.
Wire-wound resistor rated power series is (W): 1/20, 1/8, 1/4, 1/2, 1, 2, 4, 8, 10, 16, 25, 40, 50, 75, 100, 150, 250, 500
Non-wound resistor rated power series is (W): 1/20, 1/8, 1/4, 1/2, 1, 2, 5, 10, 25, 50, 100
4. Rated voltage: The voltage converted from resistance and rated power.
5. Maximum working voltage: the maximum continuous working voltage allowed. When working at low pressure, the maximum working voltage is lower.
6, temperature coefficient: the relative change in resistance value caused by each temperature change of 1 ℃. The smaller the temperature coefficient, the better the stability of the resistor. The resistance value increases with increasing temperature as a positive temperature coefficient, otherwise it is a negative temperature coefficient.
7. Aging coefficient: The percentage of relative change in the resistance value of a resistor under a long-term load of rated power. It is a parameter that indicates the life of the resistor.
8. Voltage coefficient: within the specified voltage range, the relative change of the resistor for each 1 volt change in voltage.
9. Noise: An irregular voltage fluctuation in the resistor, including thermal noise and current noise. Thermal noise is caused by irregular free movement of electrons inside the conductor, which causes the voltage at any two points of the conductor to change irregularly. .
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