Trimmer potentiometers and preset resistors are small variable resistors which are used in circuits for tuning and (re)calibration.

Types of Trimming Potentiometer

Several different versions of trimmer are available, using different mounting methods (through hole, smd) and adjusting orientations (top, side) as well as single and multi-turn variation.

1》Open, carbon track
2》Enclosed, side adjust
3》Enclosed, SMD

Single turn

Single turn trimmers/presets are very common and used where a resolution of one turn is sufficient. They are the most cost effective variable resistors available.

Multi turn

For higher adjustment resolutions, multi-turn Trimming Potentiometers are used. The amount of turns varies between roughly 5-25, but 5, 12 or 25 turns are quite common. They are often constructed using a worm-gear (rotary track) or (linear track) mechanism to achieve the high resolution. Because of their more complex construction and manufacturing, they are more costly than single turn preset resistors. The lead screw packages can have a higher power rating because of their increased surface area.

Trimming potentiometer symbols

The following IEC symbols are used for trimmers and preset resistors. Although this are the official symbols for occasionally adjusted resistors, the standard symbols for a potentiometer or rheostat are often used.