1. Preparation and visual inspection

• 1. Power up all test instruments 30 minutes in advance;
• 2. Test air supply at 0.6 ± 0.1 MPa;
• 3. No visible damage on the actuator; copper air lines free of dents, firmly fitted;
• 4. Position-transmitter connecting-screw length must match the actuator model; the plane formed by the link fixed on the transmitter shaft and the connecting screw must be perpendicular to the horizontal.

2. Test standards and methods

• 1. Fix the actuator on the test bench; connect supply air, control air and the travel-detection link; calibrate the bench instruments;
• 2. Mechanical zero: apply 4 mA (0%): control air should be 0.02 MPa and piston travel zero. If not, adjust via the nut on the zero screw (too high — tighten). Zero and span need repeated adjustment; zero error ≤ 1%;
• 3. Mechanical full span: apply 20 mA (100%): control air should be 0.10 MPa and piston travel at maximum. If not, adjust the span spring (span small — loosen; span large — tighten). Full-span error ≤ 1%;
• 4. Mechanical mid-travel: after zero and span, apply 12 mA (50%, 0.06 MPa) and adjust the transmitter link so it stays perpendicular to the horizontal at this point;
• 5. Full-travel deviation: from 0.02 MPa (0%) step through 0.036 (20%), 0.052 (40%), 0.068 (60%), 0.084 (80%), 0.1 MPa (100%) over the full stroke; deviation at each point ≤ 1.5%;
• 6. Nonlinearity test: from 0.02 MPa (0%) raise to 0.10 MPa (100%) then back down, recording stroke at each step; nonlinearity against the theoretical pressure–stroke curve ≤ 1% (※);
• 7. Hysteresis test: same method; for the same pressure the maximum difference between up and down strokes ≤ 1%;
• 8. Sensitivity test: at 0.03, 0.06, 0.09 MPa stroke points, increase and decrease pressure and measure the signal change needed to start 0.1 mm of stem movement; maximum change ≤ 0.2%;
• 9. Cylinder tightness: apply 0.5 MPa to either chamber, shut off supply; pressure drop within 10 minutes must not exceed 0.01 MPa (※);
• 10. Transmitter electrical zero: open the transmitter cover and wire it; apply 12 mA (0.06 MPa) and turn the internal eccentric so its black line aligns with the white line on the board; then apply 4 mA (0.02 MPa) and adjust the zero potentiometer until the output reads 4 mA; electrical zero error ≤ 1%;
• 11. Transmitter electrical span: apply 20 mA (0.1 MPa) and adjust the span potentiometer until the output reads 20 mA; span error ≤ 1%;
• 12. Feedback current over full travel: 4 mA (0%), then 8 (25%), 12 (50%), 16 (75%), 20 mA (100%). Allowing for the nonlinearity of linear-to-angular conversion: error at 0/50/100% ≤ 1%, at 25/75% ≤ 2%;
• 13. Feedback current hysteresis: as for the cylinder test; maximum stroke difference at the same feedback current ≤ 1%;
• 14. Complete the calibration record sheet item by item; the tester must sign;
• 15. After all tests pass, refit the transmitter terminals, tighten the rear cover and plug the positioner air inlet with the plastic cap.

※ These items may be skipped at discretion.

Related Reading

• Fisher Pneumatic Actuator Commissioning
• How a Pneumatic Valve Positioner Works