17-12 Setup > Calibrate
Press | twice, then select Calibrate: | |
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Speed
This calibrates the speed from a paddlewheel sensor connected to the 657. Calibration may be required because different hull shapes have different flow characteristics. Obtain an accurate measurement of the boat’s speed from a GPS receiver; or by following another boat travelling at a known speed; or by making a timed run over a known distance.
Note: for accurate calibration:
•The speed from a GPS receiver should be greater than 5 knots.
•The speed from another paddlewheel transducer should be between 5 and 20 knots.
•Best results are achieved in calm conditions where there is minimal current (best at high or low tide).
Calibrating speed:
1Travel at a constant, known speed.
2 In the Calibrate menu, select Speed.
3Press 
or 
to change the displayed speed to the true value.
4Press 
.
Speed filter
Waves and wind cause the boat speed from the paddlewheel transducer to fluctuate slightly. To give stable readings, the 657 calculates these values by taking several measurements and averaging them. Set the Speed filter to the lowest value which gives stable readings. The range is 1 to 30 seconds or Off (0).
Temperature
The factory settings should be sufficiently accurate for normal usage. To calibrate the temperature readout, first measure the water temperature with a thermometer known to be accurate.
Use the cursor keys to display the temperature readout box, then increase or decrease the value to match the measured temperature. The temperature can be set from 32° to 99.9°F (0° to 37.7°C) with a resolution of 0.1° unit.
To change the units between °F (Fahrenheit) or °C (Celsius). (see section
Temperature filter
Water turbulence and currents cause the water temperature to fluctuate slightly. To give stable readings, the 657 calculates these values by taking several measurements and averaging them. Set the Temperature filter to the lowest value which gives stable readings. The range is 1 to 30 seconds or Off (0).
72 | Northstar Explorer 657 Installation and Operation Manual |