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For shipboard applications, install the sensor near the center of gravity. For all applications, it is
preferable to install the device where linear dynamic effects are minimized.
Power:
The unit requires a regulated
15 VDC dual power supply (0.6 Watts). STABLE POWER IS
±
REQUIRED. The system is sensitive to power supply changes.
Theory of Operation
In order to obtain an accurate signal in both the short-term and in the long-term, the Vertical
Reference relies upon an Angular rate sensor combined with a solid-state pendulum. Integrating
the angular rate output generates the position output. This signal is compared with the output from
the pendulum and the resultant error signal is passed through a long time constant filter and fed
back as a bias to the rate sensor. Sending a portion of the error directly to the position integrator
damps the system. By using a long time constant, the effect of the short-term errors in the
pendulum is minimized. Thus, the adverse effects of inertia, damping and short-term lateral
accelerations on the pendulum essentially do not show up on the vertical reference output. See
Figure 1 for system overview.
Figure 1
The solid-state angular rate sensor has a sensing mechanism consisting of a piezoelectric transducer
element in a "tuning fork" configuration. The two drive elements are resonantly driven in opposite
directions. When a rotation occurs, the momentum stored in the vibrating elements causes an out-
of-plane bending force that is demodulated to accurately depict the rotation rate.
Since the output of the vertical reference involves the synchronizing of an integrator to a reference,
a rotation exceeding either the full scale limits of displacement or angular rate could greatly disturb
the synchronization and produce large errors. Returning the unit to a displacement and angular rate
within range would allow the unit to again synchronize. Depending on the extent of output
saturation, the synchronization will occur in less than sixty (60) seconds.
Watson Industries, Inc.
ADS-C232-1A Rev G 04/24/2023
4
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