Rate of Turn Zero Offset Calibration. Maretron DSM250-01

Figure 175 – Programming SSC200 Rate of Turn Damping Period

6.22.8 Rate of Turn Zero Offset Calibration

The DSM250 is capable of displaying rate of turn information from a Maretron SSC200 compass.

Although the compass provides very accurate rate of turn information, it can drift off of zero even though the vessel is not turning. Fortunately, the SSC200 can learn the zero offset for different conditions found on the vessel. You teach the compass these zero offset values by pressing the

Enter key ( ) with the “Rate of Turn Zero Offset Calibration…” menu item selected which causes

the DSM250 to display the screen shown in Figure 176. The Rate of Turn Offset Calibration should

be done before the Deviation Calibration (section 6.22.5).

Figure 176 – SSC200 Rate of Turn Zero Offset Calibration Screen

6.22.9 Variation Source Entry

The SSC200, being a magnetic compass, transmits heading information referenced to the magnetic north pole (magnetic heading). The SSC200 is capable of transmitting heading information referenced to the earth’s geographic North Pole (true heading). In order to produce true heading,

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DSM250 User’s Manual information regarding the magnetic variation at the current location is required. Please see the

SSC200 User’s Manual for more details on the use of magnetic variation by the SSC200 compass.

By default, the SSC200 is capable of receiving variation information on either its NMEA 0183 or

NMEA 2000

® interfaces. This causes the SSC200 to use variation data from either the NMEA 0183 interface or the NMEA 2000 ® interface.

Figure 177 – Setting Variation Source to NMEA 0183 or NMEA 2000

®

(factory default)

You should need to alter this setting only if:

• There are variation sources available on both the NMEA 2000 ®

• There is no magnetic variation source available.

and NMEA 0183 interfaces, or

If variation sources are available on both the NMEA 2000 ® and NMEA 0183 interfaces, you must tell

the SSC200 which source to use. Figure 178 below shows the NMEA 0183 source selected. This

causes the SSC200 to use variation data from the NMEA 0183 interface and ignore all other variation sources (i.e., NMEA 2000 ® interface and manual entries).

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Figure 178 – Setting Variation Source to NMEA 0183 Only

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Figure 179 below shows the NMEA 2000

® source selected.

Figure 179 – Setting Variation Source to NMEA 2000

®

Only

If there is no magnetic variation source available on either the NMEA 2000 ® or the NMEA 0183 interface, and you wish to display true heading information, you may manually enter a magnetic variation. To set a manual variation value, you must change the variation source by pushing the Enter key ( ) with the “Variation Source:” menu item selected. This highlights the next field where you select “Manual Entry:” by scrolling ( or ) through the options until you reach “Manual Entry:”.

Pressing the Enter key ( ) with the “Manual Entry:” menu item selected takes you to the screen

shown in Figure 180.

Figure 180 – Entering Manual Variation

Press the Scroll Up ( ) or Scroll Down ( ) key to change the amount of East or West variation.

Press the Accept Key ( ) when the desired number is shown. You may also disable manual variation by setting the value to “Disable”; this option appears between the values 0.0°E and 0.1°W when scrolling through the values. When manual variation is disabled, the SSC200 will not transmit any variation information and heading information will be available only in magnetic heading format.

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DSM250 User’s Manual

WARNING: Magnetic variation changes as your location on the earth changes; therefore magnetic variation should be adjusted with changes in position. Neither the DSM250 nor the

SSC200 will make these changes automatically; they are the responsibility of the user.

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