Variable Resistors ตัวต้านทานปรับค่าได้

POTENTIOMETERS

A potentiometer is a variable resistor whose resistance value can be changed by moving a sliding contact or wiper along its resistive element to pick off the desired value. A potentiometer has terminals at each end of its fixed resistive element, and the third terminal is connected to a moveable wiper. If the wiper is moved back to the beginning of the resistive element, the potentiometer’s resistance value is minimal, but if it is moved across the full length of the element, the value reaches its maximum. There are three different mechanisms for moving the wiper along the resistance element:



1. Sliding the wiper by finger pressure
2. Turning a leadscrew on the case to drive the wiper back and forth
3. Rotating a screw or knob attached to the wiper to sweep it around a curved element

Potentiometers for electronic circuits are classified as follows:

• Precision
• Panel or volume-control
• Trimmer

The common abbreviation for potentiometer is pot, so there is a precision pot and a panel or volume-control pot. However, a trimmer potentiometer is usually called a trimmer (to be distinguished from a trimmer capacitor). These variable resistors share the same schematic symbol and are made from many of the same kinds of materials.