Nuova Marea, NM-251A Series Data Converter

The Nuova Marea Ltd. NM-251A Series Data Converter is an NMEA-0183 data multiplier and converter for marine applications. It takes data from two NMEA-0183 inputs (with automatic primary/secondary fallback) and distributes it to multiple NMEA-0183 outputs (typically four or five RS-422/TTL ports and one bidirectional RS-232 port for PC connection). It ensures reliable data flow between various navigation instruments like GPS, autopilots, radars, and ECDIS, offering configurable output baud rates and robust, marine-certified design.

Technical Specification

Electrical Specifications:

Supply Voltage: 9 to 35 VDC (Nominal: 24 VDC)
Power Supply Protection: PTC Resettable Fuse
- $V_{ma x}$ : 60V
- $I_{ma x}$ : 40A
- $I_{h o l d}$ (23°C): 0.25A
- $I_{t r i p}$ (23°C): 0.5A
- Max time to trip (23°C): 2.2 seconds for 1.25A
Current Consumption:
- 50mA in idle state
- 150mA in full output mode

Inputs:

Number of Inputs: 2 x NMEA-0183
Isolation: Optically isolated
- Common Mode Rejection: 10kV/$\mu$sec
- Isolation: 480 Vrms
Input Resistance: Typically 1 kΩ (some sources state 1.5 kΩ, but 1 kΩ is more common in recent documentation)
Signal Levels Accepted: TTL, RS-232, RS-485/422

Outputs:

Number of Outputs:
- 5 x buffered RS-422/TTL (general purpose)
- 1 x RS-232 (bidirectional for PC connection)
- Note: One of the RS-422 outputs can also be a signal conversion from the RS-232 RXD channel, effectively acting as a fifth RS-422/TTL output.
Output Protection: Buffered for all RS-422 outputs.

NMEA Data Speeds (Baud Rates):

Input Speed: 4,800/8/N/1 (standard NMEA-0183) when in Mux or Split/Mux mode. In Fallback mode, it autosenses.
Output Speed: User selectable: 4,800, 9,600, 19,200, or 38,400 baud (8/N/1 parity/data bits/stop bits). RS-232 port can be baud rate free user selectable.

Functionality Modes:

Mux Mode: Two channel input to five output data combiner/multiplier.
Split/Mux Mode: Dual input to two output data multiplier, one output data combiner.
Fallback Mode (Input Priority Encoding): Autosense two inputs to five output data multiplier, with automatic switching from primary to secondary input if primary signal is lost for approx. 8 seconds. Automatic return to primary when signal is restored.
Watchdog Timer: Supervises input signals for correct application and ensures failsafe operation.

Indicators:

Ina LED: Indicates data overflow at input port 1 or no signal or incorrect polarity.
Inb LED: Indicates data overflow at input port 2 or no signal or incorrect polarity.
Out 1/2 LED: Indicates data transmission from output ports 1 and 2.
Out 3/4 LED: Indicates data transmission from output ports 3 and 4.
Out 5 LED: Indicates data transmission from output port 5 and RS-232 interface.

Physical & Environmental Specifications:

Dimensions:
- Width: 110mm / 134.80 mm (including mounting flanges)
- Depth: 82 mm
- Height: 43 mm
Housing: Styrene (ABS)
Degree of Protection: IP20 (for the housing itself, meaning it’s generally for indoor, protected environments, not exposed to spray or dust directly)
Compass Safe Distance: 0.90 m
Operating Temperature: -15°C to +55°C
Approvals: Certified to IEC 60945 (for use on-board SOLAS vessels), ABS Design Assessment Certificate (e.g., 08-PR299432-PDA)