SKIPPER SD21 Speed Over Ground (SOG) Speed Log With Built in STW Sensor
The SKIPPER SD21 is a Single Axis Doppler Speed Log and a Dual Axis SATLOG Combined. It is designed to meet the IMO resolution MSC334(90) which require two separate speed logs for vessels above 50 000 dwt.
The SKIPPER SD21 gives accurate navigation parameters, measured as they happen, and presented in a logical, user-friendly way.
SKIPPER DL21 Display
SD21 Specification
| Speed Log : | SD21 |
| Number of Axis : | 3+1 |
| Speed range longitudinal: | +/- 99.9 knots from Satlog +/- 50 knots from doppler speed log |
| Speed range transversal : | +/- 99.9 from Satlog N/A from doppler |
| Water track (from) : | 2 meter |
| Temperature accuracy error : | <1°C |
| Power Supply : | AC : 115-230 V 50/60 Hz |
| DC : 20-32 V | |
| Power Consumption : | – Display 5W – Elecronic unit 10W |
| Display : | – 28×30 pixle alphanumeric LEDs (red) with dimming – Multi – Panel PC 9″ touch display, resolution 800×480 |
| Mounting dimensions display : |
– Dot matrix display: 124×124 mm. Bracket or panel mounting
– Touch display: 224.5 mm wide x 140 mm high – Antenna: 100 mm height, 180 mm width and 790 mm long
|
| IP rating : | Display : 2x Antenna : 66 |
| Accuracy : | 0.2 knots or 2% whichever is greater |
| Weight : | 1.2 kgs for Graphic display 1.8 kgs for dot matrix display for STW 3 kgs for antenna
4 kgs for electronic unit
|
| Mounting options : | |
| Speed alarms : | High and low speed limits |
| Power failure | |
| Sensor failure | |
| Outputs : | 4xNMEA 0183 |
| 2xLAN (IEC61192-450) | |
| Inputs : | 2xNMEA 0183 (IEC61192-1) |
| 2xLAN (IEC61192-1) | |
| NMEA Outputs: |
|
| Classification: | IMO Wheelmarked |
| MED-B |
One Full System Consist of :
| Displays needed : | |
| SD21-SB Touch display | |
| CD402CU-SC Dot Matrix display for STW | |
|
Needed: SL-SN300-SA Satlog GPS and Glonass antenna
One of the below sensors are needed:
|
 |
|
DL1SG-SA for 60 mm Sea Valve
DL1ST-SA for Steel Tank
DL1STA-SA for Aluminium Tank
|
|
|
DL1SDB-SA for 100 mm Sea Valve
DL1SN-SA for Simrad NL-Log retrofit
DL1SS-SA for Sagem/Safran retrofit
|
|
|
DL1SV-SA for Naviknot SRD331 retrofit
DL1SX-SA for PCSV60 retrofit
|
|
| Electronic Unit : | |
| JB70SD21-SA | |
| Bottom housings : |
 |
|
SB-60-SA Sea Valve for double bottom
DB-60-SA Sea Valve for single bottom
|
|
|
ETNSTCL Steel Tank
ETNALC Aluminium Tank
|
Types of Speed Logs
Electromagnetic — These devices, also called EM logs, rely on a coil in an electromagnetic sensor. When the AC current energizes the coil, it creates a magnetic field surrounding the sensor. As a vessel moves through the water, an electrical field running perpendicular to the magnetic field is produced. The sensor electrodes detect and deliver the resulting signal representing the ship’s speed to a preamplifier, which then converts it to a digital format for viewing. This process is inexpensive and has the advantage of not requiring any moving parts. However, water salinity and temperature can affect calibration. The water flow slows down closer to the hull due to friction, affecting measurements.
Pitometer — Also referred to as a pit log, the instrument uses the principle of differential pressure to determine an object’s speed through the water. It operates by submerging a Pitot tube with an opening at the base in water. While the tube is stationary, the pressure (known as static pressure) remains constant. When the tube starts moving past the water, it creates dynamic water pressure that varies based on the velocity. The effect of static pressure is removed to obtain an accurate measurement of the dynamic pressure for calculating the speed. To achieve this, a second tube is installed near the first with an equivalent static pressure. Movement through water does not generate any dynamic pressure in the second tube. The difference between the pure dynamic and static pressure readings indicates the speed of the moving object.
Doppler — Doppler transducers rely on the Doppler frequency shift effect for estimating the speed of a moving body. A transducer produces high-frequency sound pulses toward both ends of a vessel using two transmitter windows. The reflected pulses are detected by two receiver windows located in the transducer. The time delay between the transmitted signals confirms the receipt of echoes from undisturbed water surrounding the object. The vessel’s fore/aft speed vector is estimated by processing the signal information. A pre-amplifier then transmits this information in a digital format.
Impeller — These logs function by attaching an impeller or paddle wheel to the bottom of a hull. They are employed on small yachts and other such vessels.
GPS (Global Positioning System) — A sensor accesses the GPS satellite signals to pinpoint an object’s speed, in both longitudinal and transverse directions. GPS receivers with integrated rate gyros and an antenna unit calculate the heading velocity, attitude, and course. The heading is then compared in relation to the vessel’s magnitude and direction of motion in the water. The information delivered by the satellites is processed by the system, integrating the velocity data with the longitudinal and transverse ground speeds of the vessel. Speed vectors combined with data related to the rate-of-turn assist in differentiating between the vessel’s translational and rotational movement. These are required for estimating the transverse speeds for both bow and stern as given on the docking display.
Read More Articles:
- SKIPPER DL21 Navigation Speed Logs
- Rotating LED Lantern VRB-25
- M850 Solar Powered LED Marine Lantern for 3 to 6+ NM Range
- 2-3 NM Solar Marine Lanterns
Source: globalspec.com
