Speed sensor calibration for NN3D


Furuno Fan
The NN3D MFDs have a single, linear calibration available for the speed sensor. It is unclear whether this calibration is programmed to the sensor, or merely applied to the readings inside the MFD. Clearly it is preferable to have the calibration done within the sensor so that all instruments on the N2K bus will share the same accurate speed.

The Airmar N2K speed sensors have the ability to be programmed with up to 25 piecewise linear segments. Presumably the Furuno-marketed Airmar sensors also have this ability. It would be highly desirable for the MFDs to be able to program the sensor with this advanced calibration. And I mean ALL Airmar manufactured sensors, not just those with a Furuno label.

The MFD should also reset the trip log in the sensor, if it doesn't already.

Your competitor RayMarine has the ability to calibrate the speed sensor with up to 8 points, on their new ST70 Plus display. And their MFDs support both RayMarine-branded and Airmar-branded sensors equally.
I should add that the same applies to the depth sounder smart sensor from Airmar, also available with Furuno branding. The sensor can be programmed with keel offset and water density (in effect, salt vs. fresh). As with speed, it is preferable that the sensors transmit the corrected values on the N2K bus, thus assuring that all displays show the same results.