To set the tracking filter, the diagram inTo set the tracking filter, the diagram infifigugurere 4.4.77can be summarized in thecan be summarized in the
following general rules:following general rules:
For frequencies above 100For frequencies above 100kHz as a general rule the tracking filter shouldkHz as a general rule the tracking filter should
be switched off. In principle it be switched off. In principle it can follow higher frequencies but in can follow higher frequencies but in thisthis
range amplitude errors of up to approximately 10% can occur due torange amplitude errors of up to approximately 10% can occur due to
dynamic errors.dynamic errors.
For medium velocities and frequencies, the acceleration limits of theFor medium velocities and frequencies, the acceleration limits of the
tracking filter have to be tracking filter have to be taken into consideration. The optimal settingtaken into consideration. The optimal setting
must be found with the must be found with the diagram. If the velocity or acceleration limits arediagram. If the velocity or acceleration limits are
exceeded, the tracking filter loses lock (refer toexceeded, the tracking filter loses lock (refer tose
sectctionion C.2C.2). This will). This will
cause serious signal distortions, an example of which can be seen incause serious signal distortions, an example of which can be seen in
fifigugurere 4.4.88..
The upper trace inThe upper trace infifigugurere 4.4.88shows the sinusoidal velocity signal with theshows the sinusoidal velocity signal with the
tracking filter in position OFF. The lower trace shows the velocity signaltracking filter in position OFF. The lower trace shows the velocity signal
with the tracking filwith the tracking filter in position SLOW. The tracking filter is on the limit ofter in position SLOW. The tracking filter is on the limit of
the range where it the range where it loses lock, the signal is partly distorted.loses lock, the signal is partly distorted.
IIn n tthhe e mmeeaassuurreemmeennt t rraannggees s 11 , , 5 5 aannd d 1100 , , tthhe e ttrraacckkiinng g ffiilltteerr
should be set to SLOW as a general rule.should be set to SLOW as a general rule.
Using the velocity decoder PLL-DC the tracking filter is particularlyUsing the velocity decoder PLL-DC the tracking filter is particularly
important. For technical reasons the PLL-DC is more important. For technical reasons the PLL-DC is more sensitive to dropoutssensitive to dropouts
than the decoder OVD-04. Thus the tracking filter should be set than the decoder OVD-04. Thus the tracking filter should be set to SLOWto SLOW
as long as the acceleration limit is not exceeded (refer toas long as the acceleration limit is not exceeded (refer tofi
figugurere 4.4.77).).
Figure 4.8: True velocity signal (top) and signal when the tracking filter loses lock (bottom)Figure 4.8: True velocity signal (top) and signal when the tracking filter loses lock (bottom)
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