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Introduction • On Precision Pots • General Product Definitions • Construction Details • Multiturn Precision Pots • Resistive Elements • Terminals • Shaft-Rotor Assembly • Mechanical Rotation • Mounting Methods • 3540 Family • 3590 Family • Knobpot 3600 Family • Single-Turn Precision Pots • 6537/6637 Family • 6539/6639 Family • 3680 Pushbutton Family • Special Precision Pots • Shafts • Mounting Styles • Bearings • Torque • Linearity • Wiper Load • Low Current Applications • High Rotational Speed • Angles • Additional Taps • Sealed Units • Multicup Assemblies • Envelopes •
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Useful Terms
Multicup Assemblies
When two or more potentiometers are assembled or "ganged" together with a common shaft that controls the wipers in unison, the finished product is called a "multi-cup assembly." Each potentiometer housing is called a "cup." Electrical characteristics may be identical or vary widely from cup to cup, depending on the application.
The relative alignment between the cups in a multi-cup assembly is known as the "phase" relationship. The standard single-turn phase relationship is indexed at 50% voltage ratio point. The typical phase tolerance is within the linearity specification for the specific model. The standard multi-turn potentiometer phase relationship is referenced from the CCW end. The typical phase tolerance is ±2°. Other phase and tolerances are available for specific customer applications. Please reference Figure 11.16.
Figure 11.16 |
Tracking of multiple wipers (voltage output) is specified as a percent of total applied voltage, typically 2X the linearity specification. In rheostat tracking applications, the use of multi-cup units is not recommended.
As with other modifications, there are some trade-offs for addition of multiple cups as follows:
- Torque specifications increase by approximately 75% for each additional cup
- Power rating of the assembly typically decreases by 25% for each additional cup
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