Linear pneumatic actuators are widely used and reliable in performance, and they are well received by industrial users. But to make good use of them, stroke adjustment is an unavoidable step: only when the stroke is accurate is the valve opening precise and the movement linear. Taking stroke adjustment through a positioner as an example, this article breaks the stroke adjustment method of a linear pneumatic actuator into 3 steps, with a signal and pressure reference, so that you can set it accurately and evenly.
1. Step One: Adjust the Zero Point (4mA Signal)
First set the "starting point" of the stroke accurately:
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Input a 4mA DC signal to the positioner
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Read the pressure gauge on the positioner; the value should be 0.004MPa or below, that is, close to zero
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This step brings the actuator back to the zero reference of the stroke
2. Step Two: Adjust Full Scale (20mA Signal and Span Knob)
Then set the "end point" of the stroke:
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Input a 20mA DC signal to the positioner
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Read the pressure gauge; the value should be 0.2MPa
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If 0.2MPa cannot be reached, adjust the span knob:
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Turn the knob counterclockwise → the span increases, until 0.2MPa is reached
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If it exceeds 0.2MPa, turn it back in the opposite direction (clockwise)
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3. Step Three: Five-Point Four-Segment Verification
Finally, verify repeatedly to make the stroke "even":
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Repeat steps 1 and 2 above, so that the positioner stroke matches the valve stroke
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Verify 4mA, 12mA, 16mA, 20mA at five points and four stroke segments
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The four segments of the five-point check should be equal in length to ensure good linearity
4. A Signal-to-Pressure Quick Reference
| Signal | Target pressure gauge value | Meaning |
|---|---|---|
| 4mA DC | 0.004MPa or less | Zero point |
| 20mA DC | 0.2MPa | Full scale |
| 4/12/16/20mA | Equal across the four segments | Linearity verification |
Conclusion
The stroke adjustment of a linear pneumatic actuator comes down to three words: set the zero, set full scale, check linearity. Remember two key values: 4mA for the zero point, 20mA for full scale (0.2MPa), and use the span knob for fine adjustment, so that the valve stroke is both accurate and even. For technical support with linear actuator stroke adjustment, please contact our professional service team.
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