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trimmer

The term trimmer is used for small continuously tunable capacitors or potentiometers. One therefore also speaks of trimming capacitors or trimming potentiometers. In contrast to variable capacitors and potentiometers, trimmers are adjustment components whose settings are rarely changed. Rather, they are used to compensate for minor circuit differences.

Since both adjustment components, trimming capacitors and potentiometers, are often made of cermet, they are also referred to as cermite trimmers or cermet trimming capacitors. The term Cermet is a neologism of Ceramic and Metal, which is a ceramic composite material.

Trim pot and trim capacitors for SMT, Photo: Conrad, Mercateo

Trim pot and trim capacitors for SMT, Photo: Conrad, Mercateo

Trimmers have small dimensions of a few millimeters, they are available for SMT technology and for through-hole technology. Due to the material Cermet they are relatively temperature stable. Trimming capacitors only have setting ranges for small capacitances of up to about 100 picofarads (pF). The variation ratio is about 1:5, for example between 2 pF and 10 pF. Adjustment is made by turning the adjustment screw. This changes the overlap of the two coated capacitor surfaces, increasing or decreasing the capacitance value.

Trim capacitors are available as air plate, film, ceramic, disc, spindle or immersion trimmers. They are used primarily for small- signal applications such as setting filter curves or frequency tuning of oscillators, but they are increasingly being displaced by capacitance diodes.

As far as trim potentiometers are concerned, they are designed for only the smallest power ratings of less than 1 W. Their rotation characteristic can be linear or logarithmic. Trimmers are used for fine tuning in RF filters, oscillating circuits and oscillators.

Informations:
Englisch: trimmer
Updated at: 02.09.2014
#Words: 257
Links: indium (In), contrast, ceramics and metal (Cermet), surface micromachining technology (SMT), capacitor
Translations: DE
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