Feature: Industrial
Figure 2: Due to eliminating gearing and wipers, non-contact potentiometers better absorb shock and vibration in heavy-duty applications. Along with many other control and performance features, they can be found in electric linear actuators
each move from one wrap to the next. Non-contact potentiometers read the voltage changes as well, but do so with electromagnetic sensors instead of contacting wipers. Te designer’s degree of flexibility in implanting contact or non-contact-based potentiometer position sensing depends largely on user requirements.
Designing for high resolution With contact potentiometers, the designer’s primary option for increasing resolution is modifying the gearing to correlate potentiometer turns with motor or actuator screw turns. Designers who need position feedback across a full long-stroke application might gear the potentiometer to turn less as it moves. For example, in a short-stroke application, if the customer required position information for only 40% of travel, they would sacrifice resolution because there would be less resistance change of the shorter travel time. Because the number of wraps in the coil of a contact-based
architecture is physically limited, there are only so many step changes to count, limiting the resolution of the position information it can deliver. And once a manufacturer has configured it for a specific number of turns needed to achieve the desired resolution, the design is set. Non-contact potentiometers, on the other hand, enable higher
resolution because they do not rely on physical wipers or gearing. Like contact-based potentiometers, non-contact sensors determine position by recording resistance changes across the stroke length, but instead of getting this information from a physical wiper touching a coil, they use an electromagnetic sensor that detects pulse changes in the surrounding magnetic field. Te sensor outputs this digital signal to a non-contact
potentiometer’s IC, which converts it to analogue signals for reading by the actuator’s onboard electronics, interpreted as position. Because these signals do not need to correlate with physical constraints, the non-contact potentiometer gives virtually infinite granularity in measuring the stroke position.
One of the most common methods for determining where an actuator is in its stroke uses potentiometers (pots)
Programmability into design flexibility Tis ability to record infinitesimally small voltage changes without physical contact, and manage them through a soſtware interface, makes resolution programmable. If the end user needs tighter resolution, for example, the designer can change it through the interface. For instance, if the application requires a high resolution between 0.5V and 4.5V, they can program the system to achieve that. If they didn’t need as high a resolution, they might program it to go to 2.5V at the end of the travel. Te designer can do it all with soſtware rather than physical gear reductions. Such programmability can be valuable, for example, in
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