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Fig. 1 shows an example and a diagram of a rotary potentiometer. Electrically the linear and the rotary potentiometer operate the same. The main difference is that the shaft of the rotary potentiometer converts rotary motion into a change of resistance. Some rotary potentiometers are the single-turn type while others are the multiple-turn type. The single-turn potentiometer allows the rotating shaft to move the wiper from one end of the fixed resistor to the other in one shaft rotation. It's common in this type of application to refer to the rotation of the shaft in degrees (0-360°). This means that the amount of resistance for each degree can be determined, and then the amount of measured resistance can be converted to angular displacement. For instance, if the total resistance of the potentiometer is 1000 Ω, the shaft would be measuring 180° if the resistance of the wiper to one end was 500 Ω.
Above: Fig. 1: A rotary potentiometer is shown with its electrical diagram.
The rotary potentiometer is used in applications such as indicating the position of welding turntables. A turntable is used to mount multiple parts that are to be welded. The table is indexed a specific amount so that each part is presented to a welding robot at the same location each time. The position of the turntable can be measured anywhere within 360°, and each welding position can be calculated in degrees.
