Fine-tuning the rheostat class

A trim resistor, also known as a semi-tunable resistor, is also called a variable resistor. Its main feature is continuous change within a certain resistance range. It is mainly used in circuits that do not need to constantly change the resistance.

The trimmer resistor has three lead wires, which declares that two leads connect the stator and the other leads are connected to the rotor. The resistance value between the two stator leads is the nominal resistance of the trimmer resistor. The maximum resistance between one of the stator and rotor leads is also equal to the resistor's nominal resistance.

There are many kinds of fine-tuning resistors, which can be divided into vertical trimmer resistors and horizontal trimmer resistors according to the trimming resistors. The resistors can be divided into carbon film, metal ceramic, and wire wound trimmer resistors.

(1) Carbon film trimmer resistor The resistor body material of this trimmer resistor is a carbon film. In use, the carbon film is easily worn and easily causes poor contact. This type of trimmer resistor is mostly used in less demanding consumer electronics. Such as radios, recorders, black and white televisions.

Carbon film trimmer resistance range is 5ooω-lmω, rated power is 0 · 05-0 · lw, resistance error is large, generally 30%. The maximum operating voltage in the circuit is 100v.

(2) metal ceramic trimmer resistor This trimmer resistor due to the use of cermet as a resistor material, so the performance is better than the carbon film trimmer resistor, and more used in circuits that have certain requirements, such as instrumentation. This resistor is divided into single-turn type and multi-turn type. Among them, the multi-turn type can rotate up to 20 turns, and its resistance range is loω-5mω. The single-turn rotary type rotatable angle is 230°, and its resistance range is the same as that of the multi-turn type. It can be seen that the multi-turn type fine-tuning resistor is mostly used for fine and slow resistance adjustment of a precision circuit.

(3) The wire wound trim resistor body is made of alloy wire. Since the alloy wire has good characteristics, such trimmer resistors are mostly used in circuits requiring higher precision. The resistance of the wirewound trimmer resistor is generally in the range of loω-2okω, and there are single and multiple revolutions. However, due to poor high frequency characteristics, it cannot be used in FM circuits.