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Technical Terms of Trimmer Potentiometers

Technical Terms

Carbon resistive element

Fine powders of graphite and carbon black are mixed with epoxy resin and phenol resin. This mixture is formed on an insulating substrate by means of screen-printing or the like. It is made to adhere to the substrate by heating and curing. This type of element combines high productivity and a low price.

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Cermet resistive element

Fine powders of ruthenium compound and noble metals such as Ag-Pd are mixed with glass powders having a low melting point. This mixture is formed on an insulating substrate by means of screen-printing or the like and is sintered at a temperature between 700°C and 850°C. Since the sintering temperature is high, an alumina substrate is frequently used as the insulation substrate. Compared to the carbon resistive element, the cermet resistive element provides steadier performance in environments of high temperature or humidity.

*Cermet is a compound word formed from "ceramic" and "metal." It is also called Metalglaze, a trademark of CTS.

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Terminal number

Generally, a trimmer potentiometer has three terminals numbered 1, 2, and 3. Terminals No. 1 and No. 3 are connected to both ends of the resistor, and terminal No. 2 is connected to the wiper.

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Wiper

The wiper, a component of the potentiometer, is used to change the contact position as it slides over the resistive element surface to obtain the desired resistance. It is also called a "spring contact."

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Total resistance (TR)

This is the resistance between terminals No. 1 and No. 3 measured with the wiper placed at either of the mechanical ends or beyond the electrically effective range.

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End resistance (ER)

This is the resistance between the terminal at either end of the mechanical rotation range (terminal No. 1 or No. 3) and terminal No. 2, measured with the wiper placed at that end of the range.

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Concentrated contact resistance (CCR)

This is the resistance generated at the boundary between the resistor surface and the wiper, which can be generally calculated using the following expression.

Concentrated contact resistance (CCR)

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Contact resistance variation (CRV)

This is the maximum instantaneous change of the contact resistance between the wiper and resistor generated when the wiper is moved within the electrically effective rotation range. CRV contains DC components and AC components. However, unless otherwise specified, it means AC components passing through a band-pass filter of 100Hz to 50kHz.

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Setting stability (VSS)

This indicates the stability of the setting value (degree of change). It includes resistance setting stability (RSS) and voltage setting stability (VSS).

Setting stability (VSS)

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