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6.9.1.2 Installation Description
This entry allows you to modify the NMEA 2000 installation description text strings. You can enter any information you like here, such as the date the unit was installed, or the location in which it was installed, for later reference. Tools such as Maretron N2KAnalyzer allow you to view these values later.See section 3.3.4 for details on how to enter a textual value.
6.9.2 Clear Speed Calibration
The Clear Speed Calibration configuration parameter shows you the currently used correction factor. All STW readings for the particular DST100 (indicated by the SN#) are multiplied by this number to arrive at the displayed number. You can remove the correction factor by pressing the Enter key ( 
) with the “Clear Speed Calibration:” menu item selected. And then choose “Clear” using Scroll Up ( 
) or Scroll Down ( 
) keys followed by the Enter key ( 
). This changes the correction factor back to 1 such that all subsequent STW readings are no longer adjusted before displaying by the DSM250.
6.9.3 Speed Calibration
The DST100 speed through water (STW) initial accuracy is significantly affected by the location or placement of the DST100 within the hull. The DSM250 can correct for these inaccuracies using the speed calibration procedure. You calibrate the DSM250 for the DST100 STW by pressing the Enter key ( 
) with the “Speed Calibration…” menu item selected which results in the screen shown in Figure 77.
Figure 77 – Calibrating the DSM250 for DST100 Speed through Water
The speed calibration screen shown in Figure 77 indicates the STW as measured by the DST100, which can be changed to the actual STW by following these steps. First, pick a speed where you are most concerned with the best accuracy. Next, bring the boat up to the desired speed using some other source, perhaps the GPS speed over ground (SOG). Remember that the SOG does not necessary reflect the STW because of currents, and drift due to winds, so you should do this in an area where you are sure there are no currents and calm winds. Finally, use the Increase ( 
) and Decrease ( 
) keys to adjust the display value until it matches the known speed of the boat. Press the Accept ( 
) key to accept the value when you are satisfied. If you do not wish to perform installation offset calibration at this time, press the Abort ( 
) key and the speed calibration will not
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