Vishay - Bulk Metal Foil Ultra-High-Precision Trimming Potentiometers

Vishay's new 1280G and 1285G trimmers feature a Bulk Metal Foil resistive element that possesses a unique inherent temperature and load life stability. Their advanced, virtually backlash-free (< 0.05 %) adjustment mechanism makes them easy to set quickly and accurately, and maintains that setting through temperature cycling and vibration, as well as thermal and mechanical shock.

The devices offer a multi-fingered, noble metal wiper engaging a planar surface of etched Foil for low TCR end-to-end and through the wiper. Other technologies, such as wirewound and cermet trimmers, cannot be relied upon to demonstrate an acceptable TCR through the wiper.

In addition to their low TCR and excellent load life stability, the 1280G and 1285G trimmers feature a 0.1 % typical setting stability, a wide resistance range from 10 Ω to 20 kΩ, and resistance tolerances of ± 5 % (1285G) and ± 10 % (1280G). The devices offer a 0.75-W power rating at + 25 °C and 26 ± 2 turn adjustments. For increased reliability, the trimmers provide the utmost in ESD immunity, withstanding electrostatic discharges up to 25 kV.

The devices provide unidirectional, infinite resolution, which when synthesized by a combination of an absolutely uniform resistance material, multiple wiper contact points, and multiple resistance circuit paths, yields a uniquely accurate settability of less than 0.05 %. There are no turns of wire to be traversed, causing a step function, and no contact resistance variation to cause an irregular change in resistance with mechanical adjustment.

The 1280G and 1285G devices feature gold-plated terminations with tin/lead terminations on request, and are available in panel mount versions by special order.

The low values available in Foil trimmers are uniquely linear, making them suitable for end-to-wiper circuit use (rheostat), which is not normally recommended in low values in other technologies. Because of the stability and linearity of the Foil trimmer, it is not necessary to use a buffering resistor in series with the trimmer, or a linearizing resistor in parallel with the trimmer, thus eliminating the cost of sourcing and inserting an additional component.