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How Do I Calibrate a PA Feedback Actuator for Accurate Position Control?

Calibration maps raw sensor readings to real-world position values. Without it, your position data is meaningless numbers. This article covers the calibration procedure for both potentiometer and Hall effect actuators.

Potentiometer Calibration

The potentiometer's usable ADC range depends on your specific actuator unit — two identical actuators will have slightly different min/max values. Calibrate each unit individually.

1. Drive to full retract

Power the motor to fully retract the actuator. Wait for it to stop. Open Arduino Serial Monitor and note the raw analogRead() value — this is your POT_MIN.

2. Drive to full extend
 

Power the motor to fully extend the actuator. Note the raw analogRead() value — this is your POT_MAX.

3. Store and map
 

Store POT_MIN and POT_MAX as constants. Use map(rawVal, POT_MIN, POT_MAX, 0, STROKE_MM) to convert any reading to millimetres. Use constrain() to clamp values within range.

4. Verify mid-point accuracy
 

Drive to a known mid-stroke position (e.g., 75 mm on a 150 mm stroke) and measure physically with a ruler. If the reported position differs by more than 2–3 mm, recheck the calibration or apply a correction offset.

 

Hall Effect Calibration

1. Determine pulses per mm

Drive the actuator from full retract to full extend while counting total pulses. Divide by stroke length in mm: MM_PER_PULSE = stroke_mm / total_pulses. Typical value for PA-04-HS is ~1.5 mm/pulse.
 

2. Set home position

Drive to full retract. Zero the pulse counter. This is position 0 mm. All subsequent positions are measured from this home reference.
 

3. Store calibration in EEPROM (optional)

For systems that lose power regularly, store the MM_PER_PULSE value in Arduino EEPROM so it persists across resets. The home position must still be re-established after power loss via a homing routine.
 

✅  Re-calibrate after actuator replacement Even the same model will have slightly different potentiometer min/max values unit-to-unit. Always recalibrate when swapping out an actuator.