Raymarine ST6000 Service Manual page 171

1. Description and Functional Test
The rudder reference transducer contains a single turn plastic potentiometer to
provide the course computer with rudder position information.
With the rudder reference transducer disconnected from the connector unit, its
operation can be checked as follows:-
a) Connect an Ohmeter across the blue and red wires.
b) Position the rudder reference transducer arm diametrically opposite the cable
gland and check the reading is between 2.2 and 2.8K ohm.
c) Slowly rotate the arm in both directions and check that the resistance increases
and decreases smoothly according to arm movement.
A faulty rudder reference transducer is replaced as a complete unit.
2. Resetting Centre Position
It is important that the rudder reference transducer is correctly centred to ensure that
the potentiometer output remains within the working range of the Analogue to Digital
converter (1.0V to 4.0V). During assembly, the unit is set up to ensure that when the
rudder reference transducer arm is diametrically opposite the cable gland, the wiper
is at its mid position. The installation instructions then direct the installer to mount the
transducer so that with the rudder amidships the arm is diametrically opposite the
cable gland (see figure 31). Should it be necessary to install the transducer with its
arm in an alternative position to the cable gland, the centre position of the
potentiometer must be reset as follows (see figure 32).
1. When the rudder is amidships, determine the orientation of the rudder reference
transducer arm to the cable gland.
2. Remove the plastic base plug from the underside of the transducer and connect an
ohmeter across the red and blue wires.
3. Remove the plastic cap from the top of the unit to gain access to the locking nut of
the taper collet.
4. Slacken the locking nut until the potentiometer shaft can be turned within the
rudder reference transducer cap.
5. Position the arm as determined in 1. and rotate the potentiometer shaft with a
screwdriver until the meter reads between 2.4 and 2.6k ohm.
6. While pressing the potentiometer and potentiometer mounting plate into the rudder
reference transducer body, tighten the locking nut to clamp the potentiometer shaft to
the cap.
7. Confirm the meter still reads between 2.4 and 2.6k ohm.
8. Check that the total vertical movement at the end of the transducer arm is less
than 1.5mm. If it is greater, steps 4. to 8. must be repeated ensuring that the
potentiometer and mounting plate are fully pressed into the transducer body.
9. Finally, replace the plastic plug into the base and the cap into the tap.
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