In modern circuits, various modifications of resistors are widely used. The main parameter of such elements is electrical resistance. The secondary characteristics of such parts include the maximum power dissipation and the accuracy of the nominal resistance. Depending on the possibility of changing the resistance, distinguish between constant and variable radio components of this type. The first type of this element has a certain resistance, which cannot be changed in any way. In turn, the second embodiment of such a component can change this characteristic. This class of parts includes a potentiometer, rheostats, a variable and a tuning resistor. The first two are most often used in power electronics, the last two are most often used in microelectronic devices.
According to the design, the variable and tuning resistor are divided into wire and wireless. Depending on the method of changing the resistance, distinguish between rotary and slide.
The simplest design is for a wire resistor. The dielectric ring acts as its base. A wire is wound on this element, the ends of which are attached to the 2 extreme contacts of the radio element. A handle with a slider is installed on top (it should fit snugly on the ring) and a lid with a groove for rotation with a screwdriver is installed on it. At the next stage, a central contact is established, which should connect the central terminal and the rotation element. The final stage of manufacturing such a radio component as a trimming resistor is to install the assembled structure into a protective housing. This is how the production chain of these components looks briefly. If the part belongs to the class of wireless, then the wire winding stage is skipped - the ring is made not of a dielectric, but immediately from a material with high resistance (most often it is a rare-earth material having a very high price). The cost of components manufactured in this way is greater than in the first case, and because of this they have not yet received wide distribution.
This electronic part has found the greatest application in amplification stages (with its help the gain is adjusted). A resistor with constant resistance is installed at the input, and a variable resistor at the output. After the assembly of the circuit is completed, it is with the help of the last element that the necessary gain is selected. To do this, the groove rotates until the desired cascade mode of operation is obtained. After the adjustment is completed, varnish is applied on top (on the resistor). The tuning component can accidentally rotate (from touch, from vibration, from falling) and then you have to reconfigure the circuit. To avoid this, a varnish is applied on top to fix the resistance value.
It is quite difficult to assess the importance of the role played by the tuning resistor in modern microprocessor technology (and not only). But with confidence we can say that such a radio component is used in almost all electronic devices. And trimming resistors every year are increasingly used in new circuitry solutions.