Feature: Industrial
Figure 3: Non-contact potentiometers are ideal for applications like mobile off-highway/ agricultural and factory automation/ automated guided vehicles
applications needing to change the stroke to compensate for different geometries. Actuators with contact potentiometers, for example, might return different feedback from different strokes. Correcting this would require dedicated gearing for each stroke length. With a programmable non-contact device, the designer can maintain the same feedback over the stroke, regardless of changes in geometry. A user can keep that consistency without having to modify the physical architecture. Non-contact potentiometers would also make it easier for
the designer to program more complex movement profiles, for example, seeking forward a few millimetres or making a small set of movements back and forth to zero in on a desired position. Non-contact potentiometers can be valuable in any application
requiring the actuator to move repeatedly and consistently to the exact location, such as managing the flow gate in a seeding application. In such applications, the actuator operation may be under the control of a PLC and perhaps hidden from an operator’s view, so there is no visual feedback to help determine whether the actuator has travelled far enough. Te programmability of non-contact potentiometers also
makes them excellent for developing custom applications. One part number, for example, can be programmed to handle multiple stroke lengths, making it much more efficient to test out prototypes in real-world settings.
Implementing non-contact potentiometers Non-contact potentiometers offer durability advantages, too. Eliminating the gearing in the feedback device makes for a more durable and reliable actuator. Gearing is subject to routine wear, contamination and misalignment resulting from vibration and shock. As such, they are excellent candidates for replacing hydraulic cylinders that might otherwise be specified for environmentally-challenged applications needing position control; see Figure 2.
36 March 2024
www.electronicsworld.co.uk
Non-contact potentiometers enable higher resolution because they do not rely on physical wipers or gearing
Eliminating the need for wiper contact and gearing gives non-
contact potentiometers another durability advantage over contact devices. In an application in which the actuator does not change position for an extended period, the wiper can vibrate and wear a dead spot on the coil, which would drop the signal and cause the potentiometer to fail. When this happens in a system that is running process
logic, it loses track of the position and can also interfere with some controlled moves. A movement profile that depends on a particular value will not find it, which could replace the potentiometer or the actuator.
Breaking contact Designers who have believed that non-contact potentiometers were only for high-precision applications would do well to revisit them for all applications. Even if high resolution is not critical, removing gearing from the BOM, programmable position feedback and a more rugged solution could offer significant advantages. As the design and specification process becomes more iterative
between engineering and customer teams, programmable capabilities such as the non-contact position sensing will deliver more tailored solutions in less time, without needing additional tooling.
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