| 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. |
| 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. |
| 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. |
| 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." |
| Cerastat |
A registered trademark of potentiometers manufactured and marketed by Murata Manufacturing Co., Ltd. |
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. |
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. |
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 |
= |
[(resistance between terminals 1 and 2 + resistance between terminals 2 and 3) - resistance between terminals 1 and 3)]
2 x resistance between terminals 1 and 3 |
x |
100 (%) |
|
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 100 Hz to 50 kHz. |
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).
| Resistance setting stability (RSS) |
= |
( |
resistance between terminals 1 and 2 after testing
resistance between terminals 1 and 3 after testing |
- |
resistance between terminals 1 and 2 before testing
resistance between terminals 1 and 3 before testing |
) |
x |
100 (%) |
| Voltage setting stability (VSS) |
= |
( |
voltage between terminals 1 and 2 after testing
voltage between terminals 1 and 3 after testing |
- |
voltage between terminals 1 and 2 before testing
voltage between terminals 1 and 3 before testing |
) |
x |
100 (%) |
|
