How to select and maintain fixed resistors?
( 1 ) When selecting an ordinary resistor, the fixed resistor should pay attention to the following items :
1 The rated power of the resistor should be greater than twice the actual circuit power, so that the resistor will not be burned out in normal operation.
2 Preferentially use general type resistor, such as carbon film resistor, metal film resistor, solid resistor, wirewound resistor and so on. This type of resistor has a wide range of resistance, complete specifications, variety, and low price.
3 Resistors are selected according to the installation position.
Because the material and process of making resistor are different, the volume of the same power resistor is not the same. The metal film resistor is small in size and is suitable for being installed in a circuit that is more compact in component ratio; in the case of loose element installation position, carbon film resistor can be used.
4 According to the requirements of the temperature stability of the circuit, the resistor is selected. Because the role of resistors in the circuit is not fixed, so the stability of their requirements are different, even if the resistance in the ordinary circuit has changed. The impact on the circuit work is not big; the change of the resistance will cause the change of the output voltage when the resistor is used as the voltage sampling in the voltage stabilizing circuit. Both the carbon film resistor and the metal film resistor have good temperature characteristics. The wirewound resistor can be applied in high stability, high precision and high power. Because of the special alloy wire winding, the temperature coefficient of the wirewound resistor is very small, therefore, its resistance is the most stable.
( 2 ) Maintenance and substitution of fixed resistor.
1. For carbon film resistor or metal film resistor, it is generally not repaired, but replace the same specification resistor.
2. High Power Wirewound Resistors.
For the high power small resistance wire wound resistor or cement resistor that has been broken, it is possible to cut the resistance wire and find the breakpoint, turn the resistance wire of the breakpoint back one turn and tighten it. Emergency replacement with resistance wire. The resistance wire can be removed from the old wire wound potentiometer or wirewound resistor. A resistance wire of the same resistance value as that of the original resistor is measured by a multimeter, and the resistance wire is wound on the original resistor, and the two ends of the resistance wire are respectively welded at the two ends of the original resistor ah, you can install a human circuit. When the resistance of the damaged wire wound resistor is large, the inner heat type electric iron heart can be replaced, and if the resistance value does not meet the circuit requirements, the iron core of the electric soldering iron can be adopted series and parallel methods are used to solve the problem. As long as the resistance is similar, it will not affect the normal operation of the circuit.
3. Resistance burning, can not see the color ring and resistance, and no drawings, on its original resistance can not be known, you can use the blade to the outer layer of the resistor charred paint drop, measure the resistance of one end to the burning breakpoint, and then measure the resistance of the other end to the burning breakpoint, add these two resistance values, and then look at the length of the burning breakpoint, you can estimate the resistance of the resistor.
4. Substitution.
In the repair, when a resistor is damaged, without the same specification resistor substitution, the series and parallel methods can be used for emergency treatment. Note : in adopting the method of series and parallel connection, in addition to calculating whether the total resistance meets the requirements, it is necessary to check whether the rated power of each resistor is compared its actual power in the circuit is more than doubled. In addition, the resistance of different power and resistance difference is not series-parallel. It has no practical significance.
If you want to know more, our website has product specifications for resistors, you can go to Allicdata Electronics Limited to get more information