What Is a Cermet Trimmer?
Cermet trimmers are a type of circuit component known as “semi-fixed resistors” in Japanese. Unlike variable resistors, where users must adjust the resistance value each time, cermet trimmers maintain the set resistance value even after it has been changed.
Incidentally, the term “Cermet” is a blend of ceramics and metal, and it is called cermet because it is made by blending these two types of materials. For example, it includes ruthenium oxide metal particles and glass as materials.
Uses of Cermet Trimmers
Cermet trimmers are used in circuits where resistance changes infrequent. With regular variable resistors, users must adjust the resistance value using a dial or similar method each time they use the resistor. In contrast, cermet trimmers are used, for example, to calibrate the displayed value of a measuring instrument. In this case, the resistance value is adjusted to the initial setting when the instrument leaves the factory, and afterward, the instrument is used as a resistor with a constant resistance value. Cermet trimmers are also employed in industrial equipment, medical devices, household appliances, and measuring instruments.
Principles of Cermet Trimmers
Cermet trimmers fall into the category of variable resistors, which can be carbon (carbon film), metal wire wound, or thin film. Cermet trimmers have a wide range of resistance values, excellent temperature resistance, and stable characteristics. They also allow for very smooth and subtle adjustments, with relatively low levels of noise associated with the sliding motion.
The primary components of cermet trimmers are titanium and tantalum, both of which exhibit excellent corrosion resistance. Carbon is sometimes used instead of cermet in consumer products like household appliances to reduce costs. However, for its reliability, cermet is preferred in measuring instruments, communication equipment, and medical devices. The mechanical structure used to set the resistance varies from product to product, including the position of the dial used for resistance adjustment. Electrical parameters and variable resistance ranges also differ from one product to another, so selecting the right one for the application is essential.