ACCURACY: The accuracy as with any similar system depends on the accuracy and adjustment of the compass itself. When well installed accuracy is generally within 2 degrees.
The system has an auto-calibration facility, accomplished in 2 ˝ turns of the ship.
A deviation table may be compiled and used, as with the magnetic compass itself.
The 991 system may include internal correction tables in the future.
NMEA 0183 INPUT: May connect to a GPS to receive deviation and variation corrections.
Correction is applied automatically if a GPS correction is input.
CONTROL: Internal jumper for starting auto calibration facility or on-screen control with
6 way terminal block compatible with 618/619 autopilot.
OUTPUT: Low current DIL relay. Contacts held open when all is correct.
Contacts close with loss of power and pulse if alarm condition detected.
An independently powered external audible alarm should be fitted.
A low power 5 volt alarm may be fitted to order on the 991 for OCA purpose.
CONNECTIONS: Lift off terminal blocks in the interface.
A 12 way miniature screened multicore cable is used between the interface
POWER: 12 to 30 volts at 30 VA or less.
Interface 260 x 160 x 90 mm near “Light Admiralty Grey” or “Duck Egg Green” diecast box.
991 is supplied as a trunnion mounting. A flush-mount panel is available as an extra.
The 991 is a standard unit fitted with the Magnetic compass EPROM.
OPERATION: The pick off coil interface may be used on its own (without the 991) as a replacement for previous Cetrek pick off coil systems. Generally the interface will be purpose built for use with Cetrek autopilots, leaving off the connections not otherwise required.
Currently the NMEA output from a stand-alone interface is in one degree steps.
It is in 0.1 degree steps with the full system. A proprietary Cetrek output may be used to give 1/3 rd degree steps into Cetrek autopilots.
RETRANSMISSION: To obtain stepper drive, utilise the AMI NMEA to stepper retransmission units available with 5 to 70 volts steps.
RETRANSMISSION: The 903 series synchro retransmission units turn NMEA 0183 data to synchro of ratios from 360:1 to 1:1.
TRANSMISSION: The 903-M provides this system.
NMEA 0183 DATA DISTRIBUTION
INTERFACE: 2 channels input, 10 outputs, 3 of which are isolated.
The Navtalk interface acts as a junction box allowing a neatly terminated installation.