NMEA 2000 Wind Sensors: Promise That’s Partially Fulfilled

The author tests the available N2K wind sensors and displays-all at once!-and mostly likes what he finds. A review from our September 2009 issue

September 16, 2009

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The antenna mast aboard a Down East-style powerboat makes a perfect platform for testing multiple wind sensors and displays. Courtesy Of Ben Ellison

Alas, my latest boat, Gizmo, doesn’t sail, but this 37-foot Down East-style motor vessel is a corker for testing electronics. Its overbuilt and highly accessible antenna mast easily accommodated a rack of five NMEA 2000 wind sensors. I manipulated the rack to simulate the complex motion at a real sailboat’s masthead while I monitored the instrument and multifunction displays showing the output of those sensors. It was a cat-herding exercise for sure, but I learned a lot about the gear’s similarities and differences. I also saw at least partially fulfilled the NMEA 2000 promise of easy installation and unlimited data sharing that I described in “Into the Nitty-Gritty of NMEA 2000” (July 2009; go to to read the article online).

This testing wasn’t precise enough to detect small performance differences between the sensors; I think a high-end wind tunnel and a programmable multi-ram motion simulator are required to do that comparison properly. But watching five sensors simultaneously register apparent-wind speeds all within a knot or two and measure wind angles relative to the bow to within a few degrees suggested that there wasn’t a dog in the bunch. And the test venue included the very light conditions-under 5 knots-in which I’ve personally found a wind sensor most valuable, even sail enhancing (if the instrumented boat is up to ghosting in zephyrs).

The biggest difference marking the wind systems tested is in the abilities and styles of their associated instrument displays, which range from traditional dedicated dials through limited gray-scale graphics and on into the new world of full-color all-in-ones. But thanks to NMEA 2000, indecisive sailors needn’t fret. Regardless of the sensors used, you could conceivably have some FI50 instruments from Furuno ( in your cockpit, perhaps because their power-efficient OLED screens work well in a wide variety of light conditions, and an ST70 from Raymarine ( at the nav station, perhaps largely to display all sorts of other N2K info when you’re not sailing (and/or because it can bridge in non-N2K data from Raymarine sensors that your boat may already have; see below, “Old School to New,” ). Multifunction displays also get to plug and play-with onboard computers truly joining soon-and thus the possible data/display combinations, and happy endings, are endless.


However, please note this serious caveat with regard to mixing N2K sensors and displays. Although the protocol includes optional, and rudimentary, facilities for standardizing basic calibrations, very few manufacturers so far have implemented them. Thus, if you must, say, apply an offset adjustment to your new GWS 10 wind vane from Garmin ( because it somehow didn’t get mounted dead on the bow, you’ll need a Garmin GMI 10 instrument or one of the company’s N2K-enabled multifunction displays to enter the correction. The good news is that calibration values generally reside inside the relevant sensor and, thus, are broadcast to everything on the network. But note the fudge word “generally”: Furuno instruments and multifunction displays, for instance, can apply some calibrations to any brand of sensor, which is useful except that the resulting calibrated values only show up on Furuno gear. In addition, some calibrations, such as dampening, are generally local to a specific display and aren’t stored in the dampened sensor. See what I meant about herding cats?

Along similar lines, it may be important to match the brand of your multifunction display to the brand of your N2K sensors and instruments so you can easily update all their firmware. Download the update to your home or office PC, copy it to a memory card, then stick the card into the display and, voila, the multifunction display and any familial device on the network can get new features (or fixes for bugs). Simple sensors and such dedicated displays as wind needles rarely need or get updating, but the new all-in-one instruments are quite a different story.
The Garmin GMI 10, for instance, could barely display a faux wind gauge when it first came out last year, but now it has the most feature-rich wind screens of the lot. It can chart multiple wind data points, its user-defined closehauled dial can automatically become a downwind dial when you bear off, and its interface makes it pie simple to customize these and other screens or, say, choose between water (paddle) speed or ground (GPS) speed for True Wind calculations; it can even pick which of five wind sensors you want it to listen to. I’m aware that the latter situation isn’t the usual (then again, so were my harbor mates, though that’s a tale for another day), but some belt-and-suspenders cruisers like the idea of redundant sensors, and they’ll be pleased to find their choices clearly listed by brand and model names.

Let’s note, though, an obvious twist to this N2K update game: With new software, the Raymarine ST70 or the DSM250 from Maretron ( may be able any day now to display even snazzier wind screens. Moreover, the abilities of these small, high-resolution screens and the factors involved in choosing one go well beyond wind; any standard data on the network can be illustrated and/or used in calculations. To date, I’ve seen such screen goodies as graphed depth (to indicate bottom trend), fuel flow and speed combined into real-time miles-per-gallon, and a handy time alarm function cheerfully represented as an old-time wind-up-clock icon. I found myself imagining handsome anchor-alarm graphics or a screen showing my boat’s nav-light status, blown bulbs included-all of which is possible. In fact, and though it may further complicate shopping choices, it strikes me as reasonable these days to expect your boat screens to be not only informative but also stylish, even fun, and to improve with age.


None of which is meant to slight the more traditional-looking N2K instruments developed by Furuno and Simrad ( There’s arguably no better wind sensor-to-sailor interface than those smooth-moving motor-driven needles, and besides, these gauge families aren’t as old-fashioned as they may appear. Even the dedicated dials can tap the N2K backbone for the data needed to calculate various true-wind values or for proprietary commands to, say, coordinate back lighting among same-brand instrument clusters. And Simrad’s IS20 Graphic Multifunction is actually an all-in-one unit that’s able to page through eight customizable screens and even strip chart data points or sketch-chart a go-to-waypoint.

Similarly, Furuno’s multi- and single-line digital displays can put up data you may never have seen on a “sailing” instrument before, like Beaufort Scale wind speeds or engine rpm. However, those segmented screens can’t do dot graphics and can barely explicate setup and calibration menus (unless the manual is in hand). On the other hand, they’re stunningly crisp and legible even in bright sunlight, all while purportedly using the least power of the group. (I now can precisely measures device loads; go to to read my blog reporting the loads for these wind sensors.)

In fact, I saw many screen-readability differences among the tested instruments. For instance, the Garmin GMI 10-the only sensor that uses its own 12-volt power cable instead of what’s available over the N2K backbone-is wonderfully bright in muted sunlight and belowdecks conditions, but it isn’t transflective. By comparison, the otherwise dimmer but transflective ST70 starts to shine in direct sunshine. In other words, it’s worth some effort to view instruments of interest in the sort of ambient-light conditions in which they’ll actually function, including the dark of night; boat shows, show rooms, and photographs can all be deceiving.


Significant differences exist in the design and construction of the wind sensors themselves, if not in their observed output. Garmin’s whirlygig screws directly to your masthead, which may be inconvenient if you pull the stick every winter, while Simrad’s and Furuno’s each has a slick ski-binding-like mounting bracket. But the Garmin is straight-up NMEA 2000 and reports atmospheric pressure and air temperature; an adaptor cable is needed to network the Simrad to anything but other SimNet gear; Furuno’s vane must actually cable to its wind instrument before its data even joins an N2K network.

Then there are the ultrasonic sensors, the WSO100 from Maretron and the PB200 from Airmar (, which use no moving parts. (For an explanation, see Tony Bessinger’s “Wind Speed with No Moving Parts,” a sidebar to “Sailing into the Future,” in CW’s March 2009 issue.) While the designation “PB” in the Airmar model stands for “Power Boat,” this high-end multisensor can to some extent feel its own motion and correct its wind data to compensate for its use on a sailboat. Airmar is hesitant to claim that this works well 60 feet up in a serious seaway-hence the PB designation-but at least one sailing tester who weighs in frequently at my blog (reachable via is very impressed. Panbo offers lots of info and opinion regarding the subjects discussed here, but be forewarned that some digging is required.

Finally, you might want to know about a soon-to-materialize NMEA 2000 initiative, the Third Party Gateway, that, I think, will put the cherry on the sundae for marine electronics users. During these wind-system tests, I used a Maretron USB100 gateway to pass N2K data to various charting programs on my boat’s laptop. When compared with the lash up of teensy wires and NMEA 0183 multiplexors that I’d previously needed, this arrangement was easy to set up and it worked better, but it wasn’t the promise of NMEA 2000 fulfilled. In truth, the USB 100 is translating N2K data into the older 0183 networking language, and it’s doing that because the cost of developing and certifying NMEA 2000 software has been prohibitive. The Third Party Gateway is meant to change that situation significantly, and in a year or so, developers should be able to market true N2K-to-PC gateways along with software that takes full advantage of the available data. If all goes well, consumers should see interesting sailing-performance programs, weather-data collectors, and maybe even a utility program for precisely comparing the output of five wind sensors. From this perspective, NMEA 2000’s prospects look delicious.


Old School to New

A question many sailors are asking is whether they can integrate a NMEA 2000 wind sensor or display with existing gear. The answer is “maybe.” Raymarine has been particularly innovative in this respect. Its ST70 display has SeaTalk ports in both regular style and NG (standing, in Raymarine speak, for “Next Generation,” that is, NMEA 2000) and can translate the older SeaTalk data language into NG/N2K. Hence, if you run a SeaTalk cable from an already installed ST60 system to an ST70, you’ll have a colorful new repeater for wind and other data on the system. And once connected to an N2K backbone, the same ST70 can broadcast the translated data to other NMEA 2000 displays, regardless of the brand. Raymarine also offers Wind, Speed, and Depth pods that convert the outputs of its many existing sensors into STNG/N2K format, and thus can be tied into an STNG/N2K backbone wherever that’s most convenient.

Meanwhile Simrad offers the AT10, a small and inexpensive NMEA 2000/0183 translator that’s become popular with professional marine-electronics installers. Its data-conversion abilities are limited, but wind, depth, heading, speed, and go-to-waypoint are included, and it translates both ways. It could, say, share wind info from your new N2K instrument to your non-N2K plotter or help that new instrument calculate True Wind with heading info from your existing autopilot.

Furuno has introduced the IF-NMEA2K1, a high-end and highly customizable 2000/0183 converter, and Actisense ( is about to ship the compact but able NGW-1. I plan to test both, and my hope is to see, for instance, wind data from a wireless Tacktick vane appearing on all the N2K displays and N2K depth and heading info registering on Tacktick’s wireless displays. Actisense, along with Maretron, is at work on the Third Party Gateways that may one day let your NMEA 2000 wind and other data work for you in wondrous ways.

Ben Ellison, who maintains the popular marine electronics website, is Cruising World’s electronics editor.


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