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The JRC JLN-205MK2 is an IMO type-approved, single-axis (Speed Through Water – STW) Doppler Speed Log designed primarily for commercial vessels over 300 GT requiring high-reliability speed measurement in a compact package. Unlike the touch-screen JLN-740 series, the JLN-205MK2 utilizes a 2.0 MHz high-frequency pulse Doppler ultrasonic transducer coupled with a tactile display unit (NWZ-630 or NWW-60 series), making it a workhorse for standard commercial bridge layouts and retrofit installations.
The system features advanced digital signal processing (DSP) to minimize errors caused by boundary layer micro-bubbles and water turbulence near the hull, providing stable speed readouts down to 0.02 knots accuracy at low speeds.
2.0 MHz Pulse Doppler Engine: High-frequency single-axis acoustic beams measure Speed Through Water (STW) with enhanced accuracy at low berthing speeds and high transit speeds alike.
Miniaturized Transducer Options: Uses compact, low-profile transducer elements (such as NKF-531 or NKF-543) available in flat-hull or gate-valve mounting assemblies for flexible dry-dock or underwater maintenance configurations.
High Contrast LCD Display: Features high-visibility monochrome/color LCD options with dedicated tactile rotary control and dimming buttons for high-glare daytime or dark-bridge night operation.
Flexible Sensor Output Distribution: Integrates with optional distribution buffer units (NQA-2010 / NQA-2020) to expand IEC 61162-1 serial data outputs for dual ECDIS, dual Radar, AIS, VDR, and slave repeaters.
Fail-Safe Self-Diagnostics: Continuous automated internal monitoring of transducer excitation currents and signal processor functions, outputting system alarm relay contact closures upon fault detection.
| Category | Component / Feature | Technical Details |
| System Model | Model Identifier | JRC JLN-205MK2 (Single-Axis Doppler Speed Log) |
| Measuring Principle | System Type | Single-Axis Pulse Doppler Speed Log (Speed Through Water) |
| Operating Frequency | 2.0 MHz | |
| Water Speed Range | -10.00 to +40.00 knots (Fore / Aft) | |
| Depth Below Transducer | Effective measuring depth $\ge$ 3.0 meters below transducer face | |
| Speed Accuracy | $\pm 1\%$ or $\pm 0.1$ knots (whichever is greater) / $\pm 0.02$ kn stability | |
| Distance Accuracy | $\pm 1\%$ or $\pm 0.1$ NM/hour | |
| Display & Controls | Main Display Unit | NWZ-630 / NWW-60 series (4.5″ / 5.7″ Monochrome/LCD with tactile controls) |
| Distance Display Range | 0 to 99,999.99 NM | |
| System Configuration | Core Components |
1. Main Display Unit (NWZ-630 / NWW-60) 2. Signal Processor Unit (NJC-205) 3. Transducer Unit (NKF-531 flat / NKF-543 gate valve) 4. Distribution Unit (NQA-2010 / NQA-2020 optional) |
| Interfaces & Connectivity | Standard NMEA Outputs | 2 x IEC 61162-1 / NMEA 0183 Outputs (VBW, VLW sentences) |
| Expanded NMEA Outputs | Up to 8 x IEC 61162-1 Outputs (when configured with NQA-2020 buffer) | |
| NMEA Input Ports | 1 x IEC 61162-1 GPS Input (RMC, ZDA) | |
| Pulse Outputs | 2 x Contact Closure Log Pulse Ports (200 pulses/NM) | |
| Analog Outputs | 1 x Analog Speed Voltage Output (0-10V or 4-20mA optional) | |
| Relay Alarms | Power Fail, System Fail, and Speed Limit contact relays | |
| Electrical & Physical | Power Supply Input | 100 / 115 / 200 / 230V AC $\pm 10\%$ (50/60 Hz), or 24V DC |
| Power Consumption | Approx. 35 W (AC) / 25 W (DC) | |
| Operating Temperature | -15°C to +55°C (Transducer: -5°C to +35°C) | |
| Standards & Approvals | Certifications | IMO MSC.96(72) Compliant, MED Wheelmark, IEC 61023, IEC 60945 |
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