Autohelm Inboard Autopilots (ST6000 and ST7000 systems) Service ...

Autohelm5. Track Control interfacing.In most cases interfacing the ST7000 to either a GPS, Decca, Loran or SatelliteNavigation system is a simple and straight forward task, so long as the requirementsset out in section 6 of the installation manual are met. There are however a fewexceptions:5.1 Inverted Data.Some receivers, notably some of the Furuno range and early Navstar models,transmit data in an inverted format with respect to 5V. This is easily seen as the dataline will idle high with respect to 0V in between data transmissions. In these casesthe NMEA cable on the rear of the control unit must be wired with the red wireconnected to 5V, (this is normally available on the receiver terminal block), and theblue wire connected to the data line.5.2 Conversion of Units.The Control Unit will convert all units of distance to Nautical Miles. Therefore, anyreceivers displaying Cross Track Error or Distance To Waypoint in either Kilometresof Statute miles etc will have their data displayed on the Control Unit in NauticalMiles.5.3 Alarm Messages.Track mode has 3 alarm messages:-1. No Data If a standard N.M.E.A sentence is not received by the ST7000.2. Data Error The ST7000 has recognised the incoming data as N.M.E.A buthas detected an invalid flag. This is normally due to poor signalstrength at the receiver.3. Large XTE Cross Track Error greater than O.3NM.Errors 1 and 2 can provide valuable information as to where an installation problemmight lie. The ‘NO DATA’ message indicates the ST7000 is not receiving N.M.E.Adata due to either the receiver output not being enabled or more likely a wiring errorbetween the receiver and the pilot. The ‘DATA ERROR’ message indicates theST7000 is receiving data recognised as N.M.E.A but has an invalid flag set. This isnormally due to the receiver having a low signal strength or a high noise figure.SeaTalk Service Manual 17