MTS Series 793 - Manual (Page 67)

How to Adjust Dither
MTS Series 793 Tuning and Calibration Tuning Procedures 67
How to Adjust Dither
Dither is a small, high frequency sine wave applied to a servovalve’s spool to
improve the valve’s response to low amplitude signals by reducing sticking.
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.
There are two methods for checking and adjusting dither. Method 1 uses the
controller’s scope. Method 2 uses your hearing.
Method 1:
1. Select an access level of Tuning.
2. Remove any specimen.
Dither
(exaggerated)
Test
Waveform