What are the precautions and detection methods for using variable resistors?
1.The application of the variable resistor and the matters needing attention are as follows :
(1)The power of trimming the variable resistor is small, and can only be used for current, in an electronic circuit with a smaller voltage.
(2)The variable resistor can also be used as a potentiometer, where the three pins are connected to their respective circuits and used as a voltage divider.
(3) In most cases it is used as a variable resistor, at which time the movable piece of the variable resistor is connected to a fixed pin in the circuit board, when the variable resistor is adjusted, the resistance value can be changed only by a small knob of a rotating resistor.
(4)The failure rate of the variable resistor is relatively high, the main fault is that the contact between the moving sheet and the carbon membrane is bad, and the abrasion of the carbon film is generally not repaired, direct replacement model can be ( emergency repair mainly to clean the main ).
2.Detect a variable resistor and potentiometer
When checking the potentiometer, first of all, turn the handle to see if the rotating handle is smooth and flexible, and whether the " click " sound is crisp when the potentiometer with the switch is broken, and listen to a potentiometer internal contact points and the friction of the resistor body, such as the " rustling " sound, that the quality is not good.
When testing with a multimeter, first according to the resistance of the measured potentiometer, select the appropriate electrical barrier to detect.
( 1 ) The nominal resistance of the measuring potentiometer is measured with an ohmic stop of the multimeter, and the reading shall be the nominal resistance of the potentiometer. If the pointer of the multimeter is not moved or the resistance varies a lot, it indicates that the potentiometer is damaged.
( 2 ) Detecting the contact between the movable arm and the resistance piece is good. Use the ohm stop of the multimeter to measure the resistance of the middle foot and the two sides of the foot. The rotating shaft of the potentiometer is rotated counterclockwise, and the shaft handle is slowly rotated clockwise, the resistance value should be gradually changed, and the pointer in the meter head should be moved steadily. When moving from one end to the other, the maximum resistance should be close to the nominal value of the potentiometer, and the minimum value should be zero. If the pointer of the multimeter has a beating phenomenon during the rotation of the shaft handle of the potentiometer, it is explained that the contact is not good.
( 3 ) whether the test switch is good or bad for the potentiometer with the switch, it is normal that the on-off condition of the two contact points of the electric barrier measuring switch can be used for the multimeter. The axis of the potentiometer is rotated so that the switch is " switched on " with a " disconnect " change. If the resistance value is not zero at the " on " position, the contact of the internal switch contact is not good; if in the " disconnect " position, the resistance value is not infinite, indicating that the internal switch is out of control.
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