MTS Series 252 Servovalves - Manual (Page 36)

Series 252 Servovalve Product Information 36
Adjust the Mechanical Null
Maintenance
Do not perform the following procedure without clearing the path of motion
of the actuator.
Sudden and unexpected actuator rod movement can cause serious injury to
personnel and/or damage to equipment.
Ensure that all personnel, specimen/structures, and tools are away from the path
of motion of the actuator (crush zone).
1. Exercise the actuator.
The actuator should be exercised to warm it up. Electrical and mechanical
adjustments are more repeatable after the actuator is warmed up.
A. Select displacement control for the controller.
B. Adjust the actuator for mid-displacement.
C. Turn on electrical and hydraulic system power.
D. Define a 50%, 0.1 Hz sine wave command and allow the actuator to
warm up for approximately one-half hour.
E. After the warm up period, stop the test program.
2. Set up for null-adjustment.
A. Set the supply pressure to the normal operating pressure (typically
3000 psi).
B. The actuator should be in position control, with the reset integrator
disabled or set to zero.
C. Set the electrical valve balance to zero.
D. Monitor both command (actuator displacement command,) and
feedback (actuator position feedback.)
E. For Series 252.2X and older Series 252.3X servovalves with adjuster
pins, follow step 3 below. For newer Series 252.3X servovalves with
the null adjustment screw on the top of the valve cover, follow step 4
below.
3. Setting the adjuster pin. (Series 252.2X and older Series 252.3X
servovalves.)
A. Slightly loosen the self-locking nut.
B. Insert a 3/32-inch hex key into the adjustor pin socket. See the
following figure for the location of the adjustor pin.
WARNING