Resistor Trimmer Packages:

'A', 'B', 'C', 'D/E', 'F-L', 'M', 'N', 'O', 'P', 'R', 'S', 'T', 'V-Z'

Precision Trimmer: An accurate variable resistor. Designed for less then frequent changes [occasional]. A trimmer or trim pot is used on a Printed Circuit Board [PCB] to finalize a circuit resistance. A Trimmer may be Single Turn or Multiturn device in a surface mount [shown here] or through-hole package.
There are a number of common package styles, of which a few are shown below [Surface Mount]. Note that the actual package style makes little difference in the circuit operation. Refer here for Through-Hole Trimmers. These trimmers have a setability of less than 0.5 percent of the full range value, but they may also have a variation in contact resistance of a few hundred ohms. Check the data sheet to determine the standard resistance tolerance, which could be as high as 20 to 30 percent.

Square Body Trimmer
One of the most common body styles used for resistor trimmers. The actuator will either be top mount or side mount. With two of the leads or terminals in-line with each other on one side of the package and the remaining terminal off-set on the other side of the package.

Top mount actuator. Trimmers with a top side adjustment are used when the trimmer can not be mounted near the board edge, or when the density of components on the board is to great to allow for side adjustment. For example when the components near the trimmer are higher than the trimmer adjustment, a top mount actuator will be used.

Square Body SMD Resistor Trimmer Case Drawing
Trimmer, Off-set Leads

Side mount actuator [Rectangular body]. Trimmers with side adjustments are used when the trimmer is mounted at or near the edge of the circuit board, to allow for easy access to adjust the trimmer.

Trimmer Resistor
SMD Trimmer

Top mount actuator [4mm Square body]. The resistance range of the trimmer will depend on the material used as the wiper. The variation in contact resistance will also vary between a few ohms to a few hundred ohms. Note that what ever material that is used in these surface mount packages will be [or could be] the same material used with through-hole component. Only the packaging style is depicted as changing here.

Trimmer Resistor
Trimmer, SMD Gull-Wing

Top mount actuator [4mm Square body] Note that both of these top mount adjustment trimmers provide an adjustment scale on the face of the trimmer. Note; not all trimmer package have a scale printed on the package body.

Trimmer Resistor
Trimmer, SMD J-Lead

Related Trimmer Topics;
Editor note; In general this site treats a trimmer as a potentiometer [a 3-lead variable resistor]. Of course a trimmer is never meant to be used as often as a potentiometer, so the two do have different applications and are construct differently.

Potentiometer Manufacturers [Vendors producing resistor trimmers]
Potentiometer Derating [Design issues over termperature].

PC motherboard

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