MTS Systems FlexTest SE Service Information

Model 493.02 Controller Service
Dither
Servovalve Controls
76
Dither
Dither is a low-amplitude, high-frequency sine wave that your
controller applies to your servovalve’s spool. Dither keeps your
servovalve’s spool in motion so it operates smoothly and does not silt
up or stick to its cylinder walls. It is especially useful for tests that use
small amplitude commands or run at low frequencies.
Dither amplitude was set during installation. The signal values in your
station parameter set reflect that initial dither amplitude procedure, and
are probably adequate for your test.
The following are signs of an improper dither adjustment:
• Dither amplitude is too low—While running a sinusoidal test on
a properly tuned system, you notice that the waveform distorts at
its maximum and minimum points. This will normally be more
apparent during a test that has either a low frequency or a low
amplitude test waveform.
• Dither amplitude is too high—You hear unusual sounds, such
as hammering, squealing, or pounding coming from the test
system.
Dither adjustment
prerequisites
The following must be true. If not, go to “Getting Things Ready” on
page 74.
• The hydraulic fluid and the servovalve are at operating
temperature.
• Command compensators are turned off.
Adjusting dither
amplitude
Refer to “How to Adjust Dither ” in Chapter 2, Common Tasks of the
FlexTest SE User’s manual for a detailed dither amplitude adjustment
procedure.
Dither
(exaggerated)
Test Waveform

MTS Systems FlexTest SE Specifications

General

Brand	MTS Systems
Model	FlexTest SE
Category	Controller
Language	English