What is a Trimpot?
A trimpot or trimmer potentiometer is a small potentiometer which is used for adjustment, tuning and calibration in circuits. When they are used as a variable resistance (wired as a rheostat) they are called preset resistors. Trimpots or presets are normally mounted on printed circuit boards and adjusted by using a screwdriver. The material they use as a resistive track varies, but the most common is either carbon composition or cermet. Trimpots are designed for occasional adjustment and can often achieve a high resolution when using multi-turn setting screws. When trimmer potentiometers are used as a replacement for normal potentiometers, care should be taken as their designed lifespan is often only 200 cycles.
Types of Trimpots
Several different versions of trimpots are available, using different mounting methods (through hole, SMD) and adjusting orientations (top, side), as well as single and multi-turn variations.
The following IEC symbols are used for trimpots and preset resistors. Although these are the official symbols for occasionally adjusted resistors, the standard symbols for a potentiometer or rheostat are also often used.