What Accuracy and Repeatability Can I Expect from PA Feedback Actuators?
Accuracy (how close to the target) and repeatability (how consistently you hit the same position) are different specs — and both matter for positioning applications. Here's what PA actuators can realistically achieve.
Typical Accuracy by Feedback Type
| Feedback Type | Positional Accuracy | Repeatability | Limiting Factor |
|---|---|---|---|
| Potentiometer (PA-14P) | ±1–3 mm | ±1–2 mm | ADC resolution, electrical noise, gearbox backlash |
| Hall Effect (PA-04-HS) | ±0.5–1 mm | ±0.5 mm | Lead screw pitch granularity, pulse counting timing |
| Internal limit switch only | End of stroke only | Excellent at end-stops | No mid-stroke resolution |
💡 These are achievable values, not guaranteed specs Real-world accuracy depends on your electrical installation quality, motor driver choice, control algorithm, and mechanical factors like load-induced deflection. Under ideal conditions, potentiometer systems regularly achieve ±1 mm; Hall effect systems ±0.5 mm.
Factors That Limit Accuracy
- Gearbox backlash— All gear-driven actuators have a small amount of play in the gearing, typically 0.5–1 mm. This shows up as hysteresis — approaching a target from extension vs retraction can land at slightly different positions.
- Motor coasting— The motor and lead screw don't stop instantly when power is cut. At full speed, the actuator may overshoot the target by 1–3 mm before friction stops it. Slow down before the target position to reduce overshoot.
- Load-induced deflection— Under heavy loads, the lead screw flexes slightly. Readings taken at no-load vs full-load may differ by 0.5–1 mm.
- Temperature drift— Potentiometers drift slightly with temperature. In precision applications, recalibrate at operating temperature.
How to Improve Accuracy
- Always approach the target position from the same direction (extension or retraction) to eliminate backlash hysteresis
- Use PWM speed control to slow down within 5–10 mm of the target, reducing overshoot
- Apply a software rolling average to the ADC signal (seeReading a Potentiometer Signal)
- Add a 0.1 µF capacitor on the signal line for hardware noise filtering
- Re-calibrate after extended operation as the potentiometer wiper can wear slightly over time