This video provides an overview if the Vishay Foil Resistors range of trimming potentiometers a.k.a. 'trimmers'. Trimmers are mechanically driven, variable resistors. A wiper is moved across the resistance element, picking off an intermediate voltage in the potentiometer mode, or adding resistance in the rheostat mode. Its inherent mechanical aspects have caused some users to avoid designing with trimmers and are of special concern when selecting trimmers for precision applications. However, with VFR trimmers there is a smooth, unidirectional, and infinite resolution adjustment for lower ohmic values and somewhat lesser resolution for values 5 kΩ and above. Foil also achieves a very low TCR end-to-end, and the TCR though the wiper can be specified (and is also relatively low). Further, the unique element resistive pattern design minimizes the capacitive and inductive reactance levels.
The trimmers’ advanced virtually backlash-free adjustment mechanism makes them easy to set quickly and accurately, while firmly maintaining their value. The contact resistance variation is now reduced through the use of a multi-fingered wiper on a planer surface —a comparison between the competing technologies shows these capabilities in the figure below.
Four key points:
1. Foil trimmers are preferred for precise adjustment
2. Foil trimmers are preferred when the adjustment must be
stable with mechanical vibration and temperature excursion
3. Foil trimmers introduce the least noise
4. The applied O-ring seal is the surest protection against
Vishay Foil Resistors trimmers have become the devices of choice for precise adjustment.