Adjusting The Mechanical Null; Adjust The Mechanical Null - MTS Systems Landmark 370 Series Product Information

Maintenance
I. Remove the filter O-ring from the filter.
J. Remove the filter.
K. Lightly lubricate the filter O-ring with clean hydraulic fluid, install it on the replacement
filter, and insert the filter into the housing.
L. Lightly lubricate the filter plug O-rings with clean hydraulic fluid, install them on the
filter plug, and install the filter plug.
M. Secure the filter cover plate to the housing using the four socket head screws and
washers removed in Step f. Tighten each socket head screw until it is firmly seated
against the filter cover plate. Using the appropriate sequence, tighten the socket head
screws to 4.5 N·m (40 lbf·in). Continue using the sequence and tighten the socket
head screws to a final torque of 9.60 N·m (85 lbf·in).
2. Turn on electrical and hydraulic system power.
3. Apply low hydraulic pressure to the servovalve so that hydraulic fluid gradually fills the filter
cavity.
4. Apply high hydraulic pressure and check for leaks.

Adjusting the Mechanical Null

This procedure describes how to adjust the mechanical null for the Series 252 Servovalve. The
mechanical null adjustment aligns the servovalve spool to a position that allows little or no actuator
movement when there is no control signal.
Prerequisites
Read this procedure before attempting to adjust the mechanical null. The mechanical null adjustment
is quite sensitive, and you should be familiar with the hazards that can be encountered when
performing the procedure.
Perform the servovalve mechanical null adjustment after the valve balancing procedure (electrical
compensation) has been completed and the results are judged unsatisfactory.
During the servovalve mechanical null adjustment procedure, the actuator must be able to move
through full displacement in either direction without contacting a reaction surface.
Valve Balance Adjustments
MTS controllers have an electronic mechanical null adjustment called valve balance. The valve
balance adjustment is a convenient way to compensate for a servovalve that needs a mechanical null
adjustment. The adjustment introduces an electrical offset signal that causes the servovalve to hold the
position of the actuator when a zero command is issued.

Adjust the Mechanical Null

Warning:
Sudden and unexpected actuator rod movement can cause serious injury to personnel and/or
damage to equipment.
118 MTS Landmark™ Tabletop Load Units - Product Information