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Purpose designed by Navitron Systems Limited for professional use on Magnetic and/or Gyro based commercial vessels of all types to approximately 2000 gross registered tonnes, the Navitron NT921G is a powerfully equipped and technologically advanced Autopilot which is R.M.R.S and Morsviasputnik Type Approved to IMO and ISO specifications.
A Type Approved installation programmable Autopilot for Mag and/or Gyro based vessels from 18m to approximately 2000 gross registered tonnes.
Fully programmable to provide optimum installation flexibility and final seagoing performance, the NT921G Autopilot is also simple to operate via a clearly defined ‘push and rotate’ Heading selector supplemented by +1°/-1° keys for fine course adjustment use when appropriate.
Track steering based on Cross Track Error (XTE) data received from the ships GPS system is also a standard feature providing automatically corrected direction over the ground between predetermined waypoints.
The control unit is suitable for console or bracket mounting in bridge or wheelhouse locations. Standard system supply also comprises a Mag Heading Sensor Coil and Rudder Reference Unit for installation to low voltage solenoid operated (11-40Vdc max) hydraulic steering systems.
High voltage solenoids (110/220Vac/dc) can also be accommodated via the inclusion of an optional Universal Relay Box type NT920URB.
A second Mag input facility is provided to accept NMEA heading data from a proprietary source and dual Gyro input ports are standard to accept NMEA and/or 1:1 isolated Synchro heading data.
Where Step by Step, M-type or non 1:1 Synchro ratios are involved, a Fully Type Approved Gyro interface (type NT925HDI) is available. Similarly, fully Type Approved Analogue and Dual Steering Interfaces are available for Azimuth propulsion units and Dual rudder systems respectively. (See Interface types NT990ASI and NT990DSI)
Optional Equipment
| Parameter | Specification |
| Supply Voltage Range | $11\text{V DC}$ to $40\text{V DC}$ (Main power supply with built-in power failure monitoring) |
| Power Consumption | $2.5\text{W}$ @ $24\text{V DC}$ ($8.1\text{W}$ max with full panel illumination) |
| Solenoid Drive Outputs | Solid-state FET switching outputs ($11\text{–}40\text{V DC}$, $5\text{A}$ max rating) |
| Switching Polarity | Selectable Common $+VE$ or $-VE$ |
| Optional Drive Modules | Compatible with Navitron Galvanic Isolated Drive Cards (for proportional valves / hydraulic pumps) |
| Display Panel | Red illuminated control panel with digital heading/ROT display & bargraph rudder angle display |
| Interface Type | Supported Protocol / Signal | Resolution |
| Mag Heading Input 1 | Direct Navitron Sensor Coil (HSC1 or HSC2) mounted to magnetic compass |
$0.25^\circ$ |
| Mag Heading Input 2 | NMEA 0183 ($xxHDM, $xxHDG, $xxHCC, $xxHDT) |
$0.1^\circ$ |
| Gyro Heading Input 1 | Isolated 1:1 Synchro (with $400\text{Hz}$ excitation from autopilot) | $0.25^\circ$ |
| Gyro Heading Input 2 | NMEA 0183 ($xxHDT, $xxHDM, $xxHDG, $xxHCC) |
$0.1^\circ$ |
| Track Steering Input | NMEA 0183 ($xxHTC, $xxHSC, $xxAPB) via Plotter / ECDIS |
— |
| Follow-Up Rate | Minimum $30^\circ/\text{sec}$ for all heading input types | — |
| Output Type | Configurable Formats & Sentences |
| NMEA 0183 Output |
Isolated RS-422 interface • Heading: • Status / VDR: • Selectable Update Rates: $1\text{Hz}$, $10\text{Hz}$, or $20\text{Hz}$ |
| Furuno Format | Selectable $5\text{Hz}$ or $40\text{Hz}$ update rate ($0.166^\circ$ or $0.1^\circ$ resolution, $5\text{V}$/$12\text{V DC}$) |
| Step-by-Step | Selectable $3$, $6$, $12$, or $24$ steps per degree ($5\text{V DC}$ signal amplitude) |
| Navitron Serial Data | Dedicated data line to Navitron digital repeaters / remote displays |
| Parameter | Specification |
| Steering Intelligence | Full P.I.D. steering algorithm with AutoTrim (automatic permanent helm) |
| Steering Modes | AUTO (Heading Control), STBY (Manual Helm), TRACK (ECDIS / Plotter Waypoint Steering), DODGE |
| Operator Controls | Rotary Course Setter, Yaw, Rudder Ratio, Counter Rudder, Rudder Limit, Turn Rate (ROT), Mode & Gyro/Mag Selectors |
| Automatic Stability | Automatic compensation for rudder speed variations / two-speed rudder systems |
| Panel Alarms | Power Fail, Off-Course, Steering System Fail, Rudder Limit, Heading Input Fail, Turn Rate Limit (includes Alarm Test facility) |
| Rudder Feedback Unit | Heavy-duty potentiometric reference unit (NT920RTU / NT990RTU) |
| Parameter | Specification |
| Control Unit Dimensions | $297\text{ mm (W)} \times 176\text{ mm (H)} \times 110\text{ mm (D)}$ |
| Weight | Approx. $3.3\text{ kg}$ |
| Operating Temperature | $-20^\circ\text{C}$ to $+60^\circ\text{C}$ |
| Compass Safe Distance | $0.6\text{ m}$ |
| Standard Scope of Supply | NT921G Control Unit, Mag Heading Sensor Coil, and Rudder Reference Unit |
Manufacturer Part Number: NT921G
Country of Origin: United Kingdom (UK)
MED Approval: Wheelmarked under MED 96/98/EC
Target Vessels: Workboats, fishing vessels, ocean-going tugs, motor yachts, and commercial vessels up to 2,000 GRT
Standards Compliance: Fully Type Approved to ISO 11674, IMO A.342(IX), and MSC 64/67 Annex 3
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