page_title: Trimmer (electronics)
section_title: Resistors
hierarchical_section_title: Trimmer (electronics) / Resistors
caption_attribution_description: English: Bourns TRIMIT® trimming potentiometer. Case is 1.25 inches (32&#160;mm) in length.
context_page_description: A trimmer is a miniature adjustable electrical component. It is meant to be set correctly when installed in some device, and never seen or adjusted by the device's user. Trimmers can be variable resistors, variable capacitors, or trimmable inductors. They are common in precision circuitry like A/V components, and may need to be adjusted when the equipment is serviced. Trimpots are often used to initially calibrate equipment after manufacturing. Unlike many other variable controls, trimmers are mounted directly on circuit boards, turned with a small screwdriver and rated for many fewer adjustments over their lifetime. Trimmers like trimmable inductors and trimmable capacitors are usually found in superhet radio and television receivers, in the intermediate frequency, oscillator and radio frequency circuits. They are adjusted into the right position during the alignment procedure of the receiver.
  Presets in electronics are adjustable components to which the user of the device has no access. They are intended to be set during manufacture or as part of maintenance and repair. A range of different passive components can be made as presets, including resistors, capacitors, and inductors.
context_section_description: Resistor trimmers generally come in the form of a potentiometer (pot), often called a trimpot.  Potentiometers have three terminals, but can be used as a normal two-terminal resistor by joining the wiper to one of the other terminals, or just using two terminals.  Trimpot  is a registered trademark of Bourns, Inc., and the device was patented by Marlan Bourns in 1952.  The term has since become generic.
  Two types of preset resistor are commonly found in circuits.  The skeleton potentiometer works like a regular circular potentiometer, but is stripped of its enclosure, shaft, and fixings.  The full movement of a skeleton potentiometer is less than a single turn.  The other type is the multi-turn potentiometer which move the slider along the resistive track via a worm gear arrangement.  The gearing is such that multiple turns of the adjustment screw are required to move the slider the full distance along the resistive track.  Some, possibly the majority, of multi-turn pots have a linear track rather than a circular one.
  multi-turn trim potentiometers exist, in which it takes several turns of the adjustment screw to reach the end value. This allows for very high degrees of accuracy. Often they make use of a worm-gear (rotary track) or a leadscrew (linear track).
caption: A linear multi-turn trimpot
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