Kongsberg Simrad IS12, Service Manual

Page: 39 / 67

Issue 1.0 09/06/03
SIMRAD
39
threshold level is reset at the end of each receive period by the microprocessor port P2.1 via Diode
D10. Any signal exceeding the threshold is passed to the microprocessor for processing.
5.2 Hand Controller PCB Assembly . Refer to Drawing Number E03721 . The
Hand Controller provides remote control of any display connected into an IS12 network.
Individuals displays may be selected in turn and, once selected, the remote keypad provides the
same services as the keypad on the desired instrument. With the exception of component labelling
the circuitry is identical to that of the generic Display PCB and no further explanation is considered
necessary.
5.3 Mast Head Unit . The Mast Head Unit detects the wind speed and direction
and provides the information to the various instruments for display and / or data manipulation.
Motherboard PCB . Refer to Drawing Number E03724 . . With the exception of component
labelling the Supply and Regulation, Microprocessor, NVM and CANBUS circuitry is identical to
that of the generic Display PCB and no further explanation is considered necessary.
Refer to Drawing Number E03934 . Wind speed is detected by a Hall Effect Device IC3 which is
triggered by 2 magnets mounted in the anemometer. The output of IC3 is fed directly to the
microprocessor ports P6.4 to 6.6.
Refer to Drawing Number E03931 . Wind angle is detected by a pair of matched linear Hall Effect
devices, IC1 and IC2, mounted in a predetermined position at right angles to each other. A
cylindrical magnet attached to the wind vane is suspended between them and the Hall Effects each
produce a voltage corresponding to the position of the magnet poles and hence the position of the
vane. The output of IC1 and IC2 are fed directly to the Microprocessor ports P7.0 and 7.1.
5.4 Compass System . The Compass Transducer detects the current bearing and provides the
data for display in both analogue and digital form.
Refer to Drawing Number E03789 . With the exception of component labelling, the Microprocessor
and Reset, Supply and Regulation, NVM and CANBUS circuitry have been previously described
and no further explanation is considered necessary.
The excitation coil of the fluxgate is driven at approximately 20KHz by anti-phase square waves
from microprocessor ports P4.6 and P4.7. The anti-phase signals are buffered by Transistors TR1
and TR2 to provide the necessary drive. A reference level of approximately 1.5v is fed to the
fluxgate coils from the junction of Resistors R25 and R26. The fluxgate coils are set at right angles
and thus effectively provide analogue Sine and Cosine output signals proportional to the currents
induced by the earth’s magnetic field. These signals are fed to two dual slope integrating analogue
to digital converters IC5 and IC6 via the electronic switch IC7. The timing of IC7 switching is
controlled by the microprocessor to provide simultaneous precision analogue to digital conversion
of both signals whilst avoiding possible errors caused by multiplexing of the inputs. The outputs of
the comparators IC5 are fed directly to microprocessor ports P6.5 and P6.6 which provide input
capture facilities. The heading is calculated by the processor and the data is output via the
CANBUS.