What Barometer [with NMEA] Do You Use ?

[Katiusha]

We have some standalone barometers on board, but want to upgrade to one with an NMEA [2000] interface. These are offered by Maretron, Airmar, Furuno (relabeled Airmar as I understand) as a part of their weather station models.

Latest Airmar model PB200 looks to have the best accuracy out of the above. Also a complete weather station with NMEA wouldn't go amiss

Do you have any suggestions or barometer preferences? I am only looking at NMEA enabled barometers though.

Thanks in advance!

[goboatingnow]

One thing to bear in mind. You need a display device that can usually display and optionally graph the results. Otherwise it's just technology for technology sake

Dave

[nigelmercier]

Originally Posted by Katiusha

I am only looking at NMEA enabled barometers...

I've got a project in mind to build one of these. What instruments do you have that can use the NMEA data?

[Katiusha]

Originally Posted by nigelmercier

I've got a project in mind to build one of these. What instruments do you have that can use the NMEA data?

As I understand [please correct me if I'm wrong] that Furuno's MFD accepts NMEA weather (as well as their MaxSea TimeZero).

[capecuddy]

If you have an Evinrude ETEC engine, use that.

[s/v Jedi]

I have the Maretron wind sensor and am very happy with it. I do not understand the remark that the Airmar would be the most accurate? My bet is that they both use so-so sensor and calibration with the help of local airport meteo is the big factor to get accuracy, not any difference between these units.

I use a Maretron display (dsm250) to graph this sensor, making it a 24h recording barograph.

ciao!
Nick.

[Ziggy]

Originally Posted by Katiusha

We have some standalone barometers on board, but want to upgrade to one with an NMEA [2000] interface. These are offered by Maretron, Airmar, Furuno (relabeled Airmar as I understand) as a part of their weather station models.

All of these are complete wind/temperature and pressure sensors. The Airmar PB200 adds a GPS and 3-axis compass. There is also a less expensive Airmar version (I forget the model number.)

Last summer we got the Garmin GMI10/GWS10 bundle. The GWS10 is a mechanical wind instrument (vane and paddle wheel anemometer) but it also incorporates a temperature and pressure sensors. The GMI10 is an instrument display, but you could use the GWS10 sensor with any other NMEA 2000 display (but there might be some issues with calibration when mixing brands). I've used it only one season, but so far it's been great. I haven't check the accuracy of the sensors--I have no standard to compare them to. I think for most people the ability to trend the temperature and barometric pressure is more important than the absolute accuracy.

A bigger question in my mind is the accuracy and reliability of the ultrasonic wind sensors in the Airmar and Maretron instruments. It would be interesting to hear some first hand experiences from people who race a lot. I have heard that the ultrasonic sensors are quite vulnerable to static electricity damage.

[s/v Jedi]

Originally Posted by Ziggy

A bigger question in my mind is the accuracy and reliability of the ultrasonic wind sensors in the Airmar and Maretron instruments. It would be interesting to hear some first hand experiences from people who race a lot. I have heard that the ultrasonic sensors are quite vulnerable to static electricity damage.

I don't have the Maretron WSO100 long enough (who has?!) to comment on reliability, but for accuracy I do know that the Maretron was designed to cope with heel and pitch while the Airmar/Furuno (=same) was designed for shore (=static) applications.

ciao!
Nick.

[Ziggy]

Originally Posted by s/v Jedi

I don't have the Maretron WSO100 long enough (who has?!) to comment on reliability, but for accuracy I do know that the Maretron was designed to cope with heel and pitch while the Airmar/Furuno (=same) was designed for shore (=static) applications.

ciao!
Nick.

Both Maretron WSO100 and Airmar PB200 claim the ability to accurately measure wind speed and direction up to 30 deg heel.

[s/v Jedi]

Originally Posted by Ziggy

Both Maretron WSO100 and Airmar PB200 claim the ability to accurately measure wind speed and direction up to 30 deg heel.

Oh.. yes, something is mentioned about that in the PB200 product sheet, but it is not stated in the specifications (while the WSO100 does include this in their specs). The whole design with compass and GPS sensors inside the same unit just screams it's a design for static/shore based installations that has been modified for marine use. Airmar recommends the unit for "large powerboats and commercial vessels", not sailboats.

I can see the value for catamarans, although I would still not want my compass and GPS at the masthead. I am still waiting on somebody reporting COG stability when rolling with this unit at the masthead. It all depends on how well the software routines correct and the averaging time cycle used. Even if the unit does this pretty good... not introducing the error by keeping GPS (and compass) low enough is always better.

The advantage I see for the Airmar unit is it's price... you get a GPS for free.

cheers,
Nick.

[Ziggy]

This review on Panbo finds the Airmar works quite well (Panbo: The Marine Electronics Weblog: Sailing with an Airmar PB200 :

"The resulting wind angle measurement stayed constant as the boat heeled and rolled underneath the sensor, even when amplified by my 50 foot high mast!"

I really don't have a stake in this comparison. I suspect both Maretron and Airmar make fine wind instruments.

[Katiusha]

My other half decided on Furuno's WS200 (relabeled Airmar PB200) for the following reasons:

1. After contacting Furuno, we confirmed that pressure accuracy is +- 2 mb and not +- 20 mb, as it's written on their brochure.

2. Its diameter is 2.83'' compared to 4.25'' Maretron's diameter.

3. It has a Pitch and Roll function that is a toy for my other half (it also works up to 45 degree of heel).

4. Specs sound better tested than Maretron's: ultra-sonic instruments will be influenced by very heavy rain and the manual shows it.

Regarding GPS and compass PGNs: we'll just ignore them or switch them off. But, should the other GPS antenna fail, we'll have a spare that's already installed (yes, a spare that swings on top of the mast, but better than nothing).

Both Maretron and Airmar are good units. There's also RO Wind 7 that we recently found out about (Radio Ocean website is still under construction, so showing a web shop's link): Ultrasonic Anemometer ROWIND 7. It's just an ultrasonic anemometer, but its interface box (Plus version) has a barometer inside. It's NMEA 0183 with interface box at NMEA 2000.

[s/v Jedi]

Originally Posted by Ziggy

This review on Panbo finds the Airmar works quite well (Panbo: The Marine Electronics Weblog: Sailing with an Airmar PB200 :

"The resulting wind angle measurement stayed constant as the boat heeled and rolled underneath the sensor, even when amplified by my 50 foot high mast!"

Oh yes, I was pointing at the compass and GPS, not the wind indication. The quote points at the 3-axis accelerometer and software that corrects measured wind angle for pitch and roll motion. I can see that work okay but I have never been bothered by my old instruments being influeced by roll (never saw pitch errors)... I always just accepted that. Autopilots, when programmed to sail to a wind angle, use an averaging function to filter out that error and this has always worked well for me too... but I never sail on a deep (like 170 degree) downwind angle on the AP so the risk of accidental gybe is not there. The question is if I would do that when my wind instrument is compensated for roll and my AP doesn't dampen... yes, I might use it in easy conditions when accidental gybe won't hurt but no, I would not use it in boisterous conditions.

Originally Posted by Katiusha

My other half decided on Furuno's WS200 (relabeled Airmar PB200) for the following reasons:

1. After contacting Furuno, we confirmed that pressure accuracy is +- 2 mb and not +- 20 mb, as it's written on their brochure.

Like somebody else already posted: it is not so much the absolute error that is interesting (because you can easily correct that in calibration procedure) but the linearity of the sensor is what is important. Lets say it's 1000mb and your sensor says it's 1000mb... that might sound perfect, right? But what when air pressure changes to 970mb.. what does your sensor report now... 970mb or 985 or 950?? those kind linearity errors are what is important for pressure sensors. They should state something like +/- 2mb for range 900-1100mb which for my example above would translate to a possible 968-972mb range when pressure becomes 970mb.

2. Its diameter is 2.83'' compared to 4.25'' Maretron's diameter.

Yes, the funny thing is that Maretron claims better accuracy because of the size and shape of the sensor (compensating for heel). A difference is that the Maretron has 3 ultrasonic elements in a 120 degree positioning compared to 2x2 elements of the Airmar.

3. It has a Pitch and Roll function that is a toy for my other half (it also works up to 45 degree of heel).

This function comes from the compass and it's what I question when used up at the masthead.

4. Specs sound better tested than Maretron's: ultra-sonic instruments will be influenced by very heavy rain and the manual shows it.

Yes, there's much more being written on-line about the Airmar. But reviews from cruisers have little to no value when they don't have a background in micro-electronics design. I have not seen a single professional, independent comparison between the two...

I am a great fan of Maretron and have their compass and GPS sensors in addition to the ultrasonic wind sensor. These three sensors match what you get from the single Airmar sensor, meaning the Airmar has a much friendlier price tag attached. IMO, this is the reason most cruisers select the Airmar. It's a bit funny when they then ignore the data from the compass and GPS sensors because that kills the price advantage... so I might have it all wrong. I do know for sure though that buyers of the separate Maretron sensors can put each in the optimal location/spot and use all that data

ciao!
Nick.

[Dockhead]

Hi Nick: This is slight thread drift, but then, perhaps not, since anyone thinking about buying one of these ultrasonic weather stations will ask the question sooner or later.

Do I correctly understand that you are using the Maretron as your primary wind instrument? Are you happy with it in that role?

Another question: for weather station use (as opposed to wind instrument), the compass in the Airmar is a good thing - because it can calculate the geographic wind direction. Does the Maretron have a way to give you that data? Using heading from your boat's heading sensor, perhaps?

I am thinking about going this way myself; hence the question. Cheers.

[s/v Jedi]

Hi Dockhead,

Yes, after finding that replacement for my old-tech B&G sensor cost $1,200.- I decided to stop spending money on it and went for ultrasonic.

I only have it for a short time but can't see a single reason why ultrasonic sensors would cause trouble. I love them.

The compass... I think the Airmar uses GPS (COG and SOG) for calculating wind-over-land. Yes, typical weather station feature. The Airmar won't do this as it's purely a sensor... a smart sensor with CPU and firmware updates... but still a sensor. So, when I see wind over land on my display, it is the display that takes data from sensors and do this calculation. All displays will do this (smart ones like Furuno, Maretron, Garmin etc.) I even think these displays will do that calculation when you feed it with already-calculated data from the Airmar weather station, meaning they only use the apparent-wind data (not sure on that though..)
So I do see advantages in the 3-axis accelerometer of the Airmar, but not for the GPS and compass, although I realize that the accelerometer is part of the compass module. Airmar also sells a combination compass-GPS sensor which makes much more sense imo.

ciao!
Nick.