Film variable resistor
time:2021-10-11The film type variable resistor is usually composed of a resistor body (synthetic carbon film), a movable contact piece (movable metal reed or carbon contact), an adjusting part and three pins (or pads), etc. Two fixed pins are connected to both ends of the resistor, and the other pin (center tap) is connected to the movable contact. The resistance value between the center tap and the two fixed pins can be changed by turning the adjusting part with a small slotted screw driver and changing the contact position between the movable contact and the resistance body.
Membrane variable resistors have three structures: fully sealed, semi sealed and unsealed.
a. The fully sealed film variable resistor, also known as solid variable resistor, is made of carbon black, quartz powder, organic adhesive and other materials, pressed into the matrix of plastic or epoxy resin and then heated and polymerized. The movable contact piece adopts carbon contact, and the adjusting part is made of plastic. The resistor and the movable contact are sealed by a metal shell (an adjusting hole is arranged above the metal shell). The utility model has the advantages of good dustproof performance and few poor contact faults.
b. The manufacturing process of the resistor body of the semi sealed film variable resistor is basically the same as that of the fully sealed variable resistor. The movable contact adopts a metal reed and is sealed by an external plastic cover. When the plastic cover is rotated, the movable contact also rotates. The variable resistor is easy to adjust, but the dust-proof performance is not as good as the fully sealed film variable resistor.
c. The non sealed film variable resistor, also known as sheet adjustable resistor, is made of carbon black, graphite, quartz powder, organic adhesive, etc. to form a suspension and coated on fiberglass board or glue board. The movable contact piece adopts a metal reed, which is provided with an adjusting hole, and no separate adjusting part is set. Its disadvantages are poor dust-proof performance, easy oxidation of contacts and poor contact with synthetic carbon film.
