Potentiometer feedback tells you where the actuator is by changing voltage as the actuator moves. That voltage only helps if you know the stroke, the feedback voltage range, and the controller input. Read it wrong and the actuator position will look precise while the math lies to you.
"Potentiometer feedback is only as accurate as your calibration and your wiring. If you skip calibrating both ends, or you run the signal line next to the motor leads, the controller will report a position that doesn't exist."
What is potentiometer feedback?
Potentiometer feedback uses a variable resistor connected to the actuator motion. As the actuator extends or retracts, the feedback voltage changes.
What is the simple explanation?
Think of it like a fuel gauge for actuator position. Low voltage means one end of travel. Higher voltage means farther along the stroke.
Use the formula below to estimate position.
Position = ((feedback voltage - minimum voltage) ÷ (maximum voltage - minimum voltage)) × stroke
What should the calculator inputs be?
Use this as a first-pass sizing tool. Then confirm the final choice against the actual FIRGELLI product page, the wiring diagram, and your real mounting geometry.
How do you use this calculator?
- Enter the real project values, not guesses from a different mechanism.
- Use measured current, load, stroke, voltage, or signal values where you can.
- Add margin for real brackets, wiring, friction, and installation conditions.
- Click Calculate to see your result.
What should you check before wiring feedback?
Check the actuator feedback type first. Potentiometer, Hall effect, and optical feedback do not behave the same way. A controller that expects pulses will not read an analog potentiometer like a voltage divider.
Run signal wires away from high-current motor wiring where you can. Noise in the feedback line makes the controller chase false position readings.
What is a simple example?
A 12-inch actuator reads 0.5V retracted and 4.5V extended. At 2.5V, the ratio is (2.5 - 0.5) ÷ (4.5 - 0.5) = 0.5.
Position = 0.5 × 12 = 6 inches extended.
Recommended FIRGELLI setup
Which FIRGELLI products fit this job?
Choose feedback hardware from the signal your controller can actually read.
Feedback Rod Linear Actuator
Use this when the project needs actuator position feedback built into the actuator body.
View Feedback Rod Actuators
Linear Potentiometer
Use this when you need an external linear position reference for a mechanism or test setup.
View Linear Potentiometers
FCB-2 Actuator Controller
Use the FCB-2 when you need controller features around feedback-based motion, presets, or synchronized actuator control.
View the FCB-2For actuator basics, start with the linear actuators guide.
What are common mistakes when using this calculator?
- Skipping end-of-travel calibration. Plugging in the actuator datasheet voltage range instead of measuring your actuator at fully retracted and fully extended. Real feedback voltages drift from the nominal numbers.
- Mismatching feedback type to controller input. A controller that reads pulses cannot interpret an analog potentiometer voltage. Confirm the actuator feedback type (potentiometer, Hall, optical) matches the controller input before wiring.
- Running feedback signal wires alongside motor power leads. Noise on the signal line makes the controller chase a position that isn't there. The voltage reading jumps, the actuator hunts, and the calculator output looks fine on paper.
- Calibrating once and trusting it forever. Mechanical wear, connector corrosion, and bracket flex shift the feedback over time. Re-verify both ends when behavior drifts.
How can you verify the calculator output is reasonable?
- Check that the feedback ratio falls between 0 and 1. If your current voltage is outside the calibrated min/max range, the actuator is either past a limit switch, miscalibrated, or the wiring is wrong. The ratio should always land inside the calibrated window.
- Measure actual extension at two known points and compare. Send the actuator to roughly 25% and 75% of stroke, measure the rod extension with a tape or caliper, and compare to what the calculator says. Disagreement points to a calibration shift or a noisy feedback line.
- Watch the feedback voltage with the actuator held still. A stable feedback voltage should not wander more than a few millivolts at rest. If it drifts or jumps, the signal wiring is picking up noise from the motor circuit and the calculated position is unreliable.
- Verify at the hard part of travel. Check feedback accuracy near the ends of stroke, not just in the middle. Sticky pots, end-stop wear, and bracket flex usually show up at the extremes first.
