ELECTRONICS
Improving Linear Actuator Design Flexibility with Noncontact Position Sensing
One of the most common methods for determining where the actuator is in its stroke uses potentiometers, also called pots, to track changes in electrical resistance or related voltage drops.
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by Travis Gilmer, Thomson Industries Inc.
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any linear motion applications that use rodstyle electric actuators require information on the position of the load at every point of travel. However, because stroke
lengths and applications vary, finding the ideal position feedback solution can be challenging. One of the most common methods for determining where the actuator is in its stroke uses potentiometers, also called pots. They
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track changes in electrical resistance or related voltage drops as the actuator extends and retracts. To function as position-recording devices, potentiometers must maintain an electrical connection to the actuator power circuit. Designers can accomplish this using contact or noncontact potentiometer architectures. Contact-based position measurement has been the simplest and most economical approach but is limited in resolution, design flexibility and durability. Noncontact architectures overcome many of those drawbacks but have traditionally been too expensive to justify for many mainstream applications. Today, however, the market for noncontact potentiometers has matured, and prices have dropped. Understanding the advantages of noncontact potentiometers will help motion system designers determine the most effective way to meet customer requirements.
The Basics
Due to eliminating gearing and wipers, noncontact potentiometers better absorb shock and vibration from heavy-duty applications. These potentiometers, along with many other control and performance features, can be found in select electric linear actuators.
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OEM Off-Highway | JULY/AUGUST 2022
Feedback voltage from a potentiometer typically changes from 0.5 VDC to 4.5 VDC as the actuator extends. Potentiometers are generally rated in ohms of resistance across their range and on the shaft’s number of turns (revolutions) from zero to full coverage. The most common units are 10k (ohms) 10 turns. As the actuator screw extends or re-
