Linear elements turn straight-line travel into a proportional signal that the controller can trust. In guided or unguided formats, a rod or slider moves a wiper along a long track, creating a smooth, ratiometric output that shows small steps without flicker. With the right element, alignment, and scaling, these sensors hold calibration across shifts and environments. If you want a quick contrast with rotary devices, read Rotary Potentiometer Working Principle.
Linear sensing shines when axes need honest stroke data. Select the element for duty and temperature, match resistance to input impedance, and keep wiper current low. Map the usable stroke to the controller span, record a baseline sweep with a few setpoints, and save that pack for quick rechecks. For multi-revolution angle coverage that pairs well with long travel, see How does a Multi-Turn Potentiometer Work.
Ratiometric Reads for Linear Potentiometers: ADC Fit and Noise Control
Accuracy starts with the element. Conductive plastic gives low noise and smooth steps at crawl speed. Wirewound tolerates heat and higher wiper current. Cermet holds tight bands over a wider temperature range. Pick a total resistance that fits the ADC and cable length so the divider stays ratiometric and quiet. Align the rod to avoid side load that can add noise and wear.
Prove the scale before the axis goes live. Map the electrical stroke to the mechanical limits with margins at both ends. Sweep slowly and log counts at 10, 50, and 90 percent. Reverse and repeat to check hysteresis. Save these traces with the ambient temperature and supply. If your operator sets coarse targets by hand, Understanding Hall Effect Joysticks For Mobile Equipment offers useful context on human input.
Element selection and contact design are key to achieving consistent results. Use a multi-finger wiper to ensure steady contact during long strokes. Keep the contact force strong enough for clear readings but gentle enough to protect the track. Watch for noise during slow movements and brief reversals to catch any early signs of wear.
Mounting is the final part of the signal chain. Use linear guides or parallel mounts to keep the rod straight. Check that the rod is straight and that the bearings are properly preloaded, then confirm the stroke force and friction. Running a short endurance test can help identify any drift before the unit is put into production.
Cable Entries for Linear Potentiometers: Glands, Strain Relief, Breathers
Plants bring washdown, dust, and vibration. Choose the right IP level, seal entries with rated glands, and add a drip loop. Where condensation is likely, add a hydrophobic breather. Verify seals with a short spray, then repeat a slow sweep to confirm scale. For valve loops that need tight trims, see ETI System: Control Valve Actuators and Positioners.
Temperature swings and shock test alignment. Run hot and cold soaks and a vibration sweep near local machinery speeds. Compare traces before and after for drift and stroke time. Bearings and rigid mounts keep alignment in place. Cable relief prevents fretting at entries and preserves signal quality.
Match elastomers and housings to site media. FKM, EPDM, or PTFE seals; coated or stainless bodies for corrosion control. Keep runs short, separate power from analog, and use twisted pairs. Land shields at one end to avoid loops. Inject a small disturbance during commissioning to confirm the reading stays steady.
Connector and cable choices affect uptime. Use sealed, keyed plugs with the right plating for current and environment. Seat gaskets square and torque to spec. Label leads, leave a small service loop, and avoid tight bends. These simple habits prevent intermittent faults during long service.
Production Examples: Linear Potentiometers in Motion Systems
View field setups that maintain stable stroke data under load. Use these snapshots to select hardware, perform quick checks, and detect drift early.
Pick and Place Axis Feedback
Use stroke data matched to cycle time. Map usable travel to counts so small that commands move the gripper cleanly. Align guides to avoid side load and added noise.
Pick and place needs honest stroke data at machine speed. Map usable stroke to cycle time so small commands move the gripper, not the noise floor. Align mounts and guides to prevent side load that raises contact noise. Keep runs short, shield the pairs, and confirm teach points with a slow crawl at shift change.
Prove the axis with a simple acceptance pack. Save a baseline sweep and log counts at pick, mid travel, and place. Record stroke time under load and a small step near each point. Trend low-speed noise and hysteresis after warmup. For noncontact operator inputs that set coarse targets, see How do Hall Effect Joysticks Work?
Web Tension and Draw Control
Web and draw control need quiet, low-speed position data. Map the usable stroke to the dancer range and the trim window. Size resistance for the ADC so the smallest move shows in counts. Keep the wiper current low. Align the rod to the dancer’s arm and avoid side load. Seal entries and keep the run short to block noise.
Prove the scale before startup. Sweep through tension setpoints and log counts at slack, nominal, and tight. Repeat in reverse to see hysteresis. Record stroke time under normal line speed. Save a baseline with ambient and supply noted. After service, replay the same points to confirm stability.
Gantry and Fixture Position Feedback
Fixtures and gantries need stroke readings they can trust. Set the rail parallelism and square the carriage to the rod. Use rigid mounts and the right bearing preload. Align couplers so the rod runs true. Add strain relief that moves, not pulls on leads. Log stroke force and friction after setup.
Confirm the scale before the build moves on. Sweep slowly and record counts at fixture datums. Reverse at the same marks to measure hysteresis. Warm the system for ten minutes, then recheck the offset. Save traces with the unit serial and ambient notes. For rotary heads on the same tool, see Rotary Potentiometer Working Principle.
Redundant Linear Feedback: Dual Channels and Plausibility
When it comes to ensuring uptime, it’s essential to implement two independent reads. One effective approach is to use a dual gang sensor or combine a linear potentiometer with a noncontact channel. By sampling both on the same time base and tying the inputs to a common reference, you can ensure more reliable measurements. Make sure to land the returns at a single bond point to maintain consistency.
It’s also crucial to map both strokes to counts per millimeter and establish a tight plausibility window for any offsets and slopes. If either of the channels crosses this window during a short averaging period, it should trigger a flag for a mismatch. To further safeguard against errors, you can implement a rate check and introduce a small dither to catch any stuck values.
Before finalizing any systems, it’s wise to plan safe fallbacks. If a mismatch persists, consider freezing the last good value or gradually ramping to a safe stage. Don’t forget to alert the operator and log the event for future reference.
During the commissioning phase, take the time to cross-plot channel A against channel B over a slow sweep. This will allow you to fit a line and accurately record the gain and offset. It’s beneficial to save these parameters in both the controller and the associated files. After any service changes, replace one channel and repeat this crucial check to ensure everything is functioning as expected.
Why Choose ETI Systems
ETI Systems specializes in designing and building sensors and motion controls for industrial plants. Our product line includes linear and rotary potentiometers, joysticks, and valve actuators. We are proud to hold ISO 9001:2015 certification, which reflects our commitment to quality.
Our engineering team collaborates closely with production, ensuring quick feedback and effective tuning of element type, resistance, taper, and mechanics to fit your specific controller and site needs. Each unit undergoes thorough bench testing to verify scale, linearity, center accuracy, and low-speed noise levels. When we ship, we include clear mounting instructions and detailed I/O information.
For commissioning, we take an organized approach that is both measured and recorded. You can request an acceptance pack, which features a baseline sweep and approach repeatability data. Additionally, we provide step response information, low-speed noise assessments, and stored scaling data. Our support also includes 2D and 3D CAD models, as well as wiring guidance.
We offer sealed and redundant builds for harsh environments. Our applications team carefully assesses duty cycles, environmental conditions, and I/O requirements. In the end, you receive a configured ETI model that ensures a smooth integration into your system.
Frequently Asked Questions
Linear sensors read straight line travel with a ratiometric scale, ideal for axes and slides. For rotary basics that contrast well, see Rotary Potentiometer Working Principle.
Pick a value that fits the ADC input and cable length. Keep the wiper current low to reduce noise and wear while preserving resolution.
Sweep slowly and log points at 10, 50, and 90 percent. Reverse and repeat to check hysteresis. Save the trace with the ambient conditions.
Match IP rating and materials to local media. Use sealed entries, breathers where needed, and confirm with a spray test and post-test sweep.
Ready to specify? Share your range, environment, and I/O. We will match an ETI Systems model that installs cleanly, scales correctly, and holds calibration.