Airmar 2018 part 2: Ultrasonic and EM speedo mysteries unraveled, plus new UDST800
Airmar’s newly announced UDST800 Ultrasonic Smart Triducer is real! I’ve held one in my freckly hand and even installed it on Gizmo. The reality of a new product would not normally be news, but the history of Airmar’s high tech ultrasonic and electromagnetic speed sensors has frustrated boaters wanting the promised precise and reliable Speed through the Water results, which should be many boaters, I think…
To be brutally frank, neither of the Airmar products described above ever materialized as presented, and the same is true for the Ultrasonic DST900 that Kees Verruijt enthusiastically photographed and explained in 2012. In fact, as he mentions, this odd situation started years earlier.
In Oct. 2009 Dan Corcoran’s great review of the Airmar CS4500 Ultrasonic speedo kicked off a discussion about how the high value of accurate STW (sometimes just called Speed, but definitely different from the Speed over Ground delivered by GPS). Sailors crave it for precise calculation of True Wind relative to water, but so do power cruisers for better miles-per-gallon fuel calculations. Accurate STW is also key to meaningful set and drift calculations.
There’s also talk in an old entry about how much better the ultrasonic technology would be as a “smart” transducer able to send data directly to NMEA 2000 networks (or to NMEA 0183). And one Panbo commenter came up with a still-live link to the Airmar DST900-EM — “Available Q3 2009” — while another pasted in an Airmar tech support note about an ultrasonic NMEA 2000 triducer about to come out as the DST900-CL (and those revelations led to a discussion about how electromagnetic speed sensing might compare to ultrasonic).
So in 2009, and again in 2012, there seemed to be at least a hard core crowd ready and willing to spend extra money to say goodbye to their paddlewheel speed sensor in favor of more accurate and reliable technology. They never got a chance to pull out their wallets. What happened?
I do not know why Airmar made several false starts in this area — there’s no upside I can think of — but I can theorize. As mentioned in my Part 1 entry about Airmar’s certified installer program, the company mostly works with OEM’s, not retail customers, and maybe trial balloons are more normal in that environment. It’s also an engineer-run company, so maybe testing trumped marketing. Perhaps, above all, the market for premium speed sensors is small, while Airmar has been relentlessly pushing out into other markets while also driving the CHIRP fishfinder revolution.
And none of this matters much now, except to hopefully clear the air and set the stage before we discuss Airmar ultrasonic and electromagnetic speed technology that really, really does exist.
DX900+ MultiLog
First, let’s consider the Airmar DX900+ MultiLog that seems related to the DX900-EM of 2009, but with the intriguing added abilities of measuring leeway and connecting via Bluetooth to apps (in addition to N2K or 0183 cabled connections). Kees broke the story at METS 2016, and I was part of the SAIL team to award it a Pittman.
Given the possibly embarrassing history, I was a little surprised that the DX900+ took a while to ship, but it is now available at outlets like iMarine (and the slick looking iOS AirmarCAST app above is available for download). In fact, occasional Panbo contributor Jeremy Anwyl bought one last summer for his latest vessel — a mighty Nordhavn 76 — and I was hoping to host a dual review with Kees reporting on his DX900+ beta testing experience aboard the awesome sloop Merrimac.
Unfortunately, neither Jeremy nor Kees have reliably working DX900+ sensors yet. It’s not worth getting deep into the details here as both cases are still being investigated by Airmar tech support, but it may be that EM is best suited to simple 12v electronic systems, or maybe that the NMEA 0183 option is preferable because then the power supply can be kept especially clean.
Also, Airmar tells me that numerous DX900+ are out in the field without reported problems, so here’s hoping an owner of this highly innovative sensor will report in about actual results. And that Jeremy and/or Kees will be able to report on working EM sensors soon.
UST800/850
So the ST900/950 ultrasonic speed sensor Kees also reported on at METS 2016 got my “Close but no… cigar” markup mockery because it didn’t actually ship until after Airmar decided that UST800 Smart Sensor and UST850 Smart Sensor titles made more sense. {Correction 2/20: some ST900/950 sensors did ship before the name change.}
I agree that UST800 is a good designation for the ultrasonic version of the ST800, but the best news is that the two UST sensors — the only difference is which standard Airmar casings they fit — are really available. The online prices starting at $918 are not trivial — Airmar does not list retail pricing — but consider this performance graph.
If I understand this graph correctly it shows a boat alternately accelerating and decelerating over about 18 minutes while speed is measured by paddlewheel, ultrasonic, and GPS. The paddlewheel fails quite badly over about 35 knots, but if you click the graph bigger and look closely, you’ll see that the paddlewheel isn’t doing very well at low speeds either.
Moreover, I think it’s safe to presume that Airmar used a clean ST800 or similar paddlewheel sensor for this test, and paddlewheel performance most definitely changes with fouling. Also, note the latency. In acceleration the Ultrasonic usually measures speeds slightly higher than the GPS and paddlewheel and vice versa as the boat slows down, which certainly suggests better responsiveness. But I’d like to see for myself…
Brand new UDST800!
When I asked about testing a UST sensor in January, I was delighted to learn that a UDST would not only be announced soon and was already in production. And, lo, there it is, posing in my shop before I took it down to the boat (and quite like the DST900 Kees saw in 2012).
The UDST800 ultrasonic triducer was also announced early this week — press release PDF here — and though it’s not yet listed at Airmar, here is the combined UDST/UST install guide PDF.
It will be awhile before I actually get to see UDST underway performance in Gizmo, but you can see on the Simrad NSS evo2 screens below that it’s real and ready to go.
I might want to retire my CS4500, in use since 2012 and still in working order, but first I would have to see some satisfied user reports. So I’ll be very interested how a UDST 800 works on Gizmo.
My CS4500 has quite severe problems with silt in the water like you find in shallow waters with lots of tidal activity (such as the Waddenzee). In these areas, I regularly have crazy readings that swing, in sort of a sinusiodal curve, between about 0.5 knots and 9 knots while going at a steady 6 knots, confirmed by GPS. Each full curve is maybe 20 seconds long. A minute later, with maybe a little less silt in the water, all is back to normal until it starts again a few minutes later. This never happens in clearer water (e.g. not once in 2.000nm of Baltic sailing of last season).
Another question I have is how fine you can calibrate it. An absolute must for me is ability to apply correction factors for multiple speed levels. In addition to that I would highly appreciate ability to apply different correction factors depending on roll of the boat (port bow or starboard bow). My boat or my install location definitely needs this – and it’s a standard boat and standard install location.
In theory, the roll-dependent correction should be no problem as there is continuous supply of roll (and tilt) via NMEA 2000 from my H2183 compass.
The last point, in my opinion, is critical for a sensor like this. It’s targeted at those that badly want precise speed. But the proposition “buy this sensor and you will have breathtakingly accurate speed” is, unfortunately, naive. You need to invest a lot of time in calibration, and, to be able to do that, you need software that allows very fine corrections in a number of different dimensions.
Otherwise it’s just a sensor that never fouls – also good, of course.
Great Entry, especially the history, it has been a long journey of product announcements. The ability to measure leeway, N2K, and bluetooth access to the sensor being particularly appealing features.
Over the years it has seemed like two different technologies were being developed by Airmar, the “EM” for example being different from how the CS4500 senses speed through water as described in a detailed product brochure.
Ben, does the UDST800 and DX900+ have the same guts/technology? Are they the same or different from the CS4500? Can the UDST800 measure leeway and accessed from bluetooth?
No, Dan, just the DX900+ can measure leeway speed/angle and also roll/pitch, as seen in AirmarCAST screens above. It’s also the only transducer with Bluetooth.
Henning, according to the UDST/UST intall guide linked to above, speed calibration is possible, but it’s vague beyond that, dependent apparently on what display you’re using in conjunction. And of course some systems can apply calibration independent of the transducer (but then it only shows up within that system, not to other N2K displays).
At any rate, this is definitely an interesting and still largely unknown aspect of these speedos. I did check Gizmo’s Maretron DSM to see if it could calibrate the UDST800 like it could the Maretron DST110 (equivalent to Airmar DST800). No dice, but maybe coming in Maretron update?
Also, I don’t buy that every boat speedo install needs multipoint calibration. I saw good results with Maretron’s calibration, though it did need to be adjusted as paddlewheel got dirty.
Plus we have not heard about real world results from Airmar’s latest ultrasonic tech. It may look a lot like what Kees saw in 2012 but I gather they’ve working on the Echo Correlation Processor:
“The UST800/UST850’s echo correlation processor has patented adaptive digital signal processing that automatically adjusts according to boat speed, water depth and water clarity for most accurate speed readup. Reliable operation in both salt and fresh water.”
Hi I have tried a DX900 plus plus in my carbon cruiser racer. I had great excitement for it, measuring leeway is a killer app. Unfortunately reality has not met expectations. Speed readings are all over the place. To check power supply issues, I disconnected all electronics and fed it directly from the batteries , reading speed via Bluetooth. Insert far from a marina to limit electromagnetic noise. It does not work I am sorry to report. Can be the carbon hull? Don’t know. Francisco
Thanks for the report, Francisco. An Airmar representative tells me that he thinks “the culprit in this case is the carbon hull” and wonders if you have worked with Airmar tech support?
http://www.airmar.com/contact.html
Raymarine sold the CS4500 for a while as a transducer option. We bought one gladly, being fed up with cleaning the paddle wheel transducer. It was installed back in 2003 and is still working, though the temperature probe failed last year. And yes, it wasn’t initially reliable in muddy water, though it always did seem to adapt with time – the Rajand River in Borneo was our haunt for some years. The Raymarine guys tell me they had a bit of trouble with these, and that we’re a lucky boat. So be it. Now I’m hoping for a DX900 for Christmas.
Ben. Developing a new electromagnetic sensor, aimed at the racing market, which is incompatible with carbon hulls, seems surprising. I will call airmar support in a few days when I have a bit of time. But the truth is that I have tried it In several conditions, making sure that the level of a electromagnetic noise was low. I was also quite careful to check that the unit was properly inserted in the sleeve. Unless I am proven wrong, I don’t think this product is up to standard for the general public. This may also explain why it was in the making for such a long time after the announcement. Regards
The Airmar situation over the last decade has been quite surprising, given we had very good and reliable sonic speed devices in 1997.
Interesting discussion on this subject on Sailing Anarchy:
http://forums.sailinganarchy.com/index.php?/topic/195989-any-data-for-triducer-versus-single-transducer-speed-accuracy/
from about post #63.
Maybe the UDST800 isn’t so hot and paddlewheels’ days aren’t over yet?
Ben,
What a coincidence that I see this article now. I just got off the phone with tech support regarding a customers failed CS4500 ultrasonic speed unit. It was not a very fulfilling call nor all that reassuring for me to continue installing these.
What I learned.
#1 There is no field test for the transducer to confirm whether it is the problem or not.
#2 There is no repair of the transducer, if it is what failed.
#3 Other than confirming 12V power at the control box there is no field test to confirm the control box is working.
#4 There is also most likely no repair to the circuit board (they were not too committal in this) of the CS4500 control box.
So, I can send it in $$ and they can possibly test it and tell me which part is bad, the transducer or control box, but then they could not confirm availability of parts for this unit. I even gave them the model revision number; 18-449-01 Rev.01
I have already confirmed it is not the display with a test unit I keep around.
These ultrasonic sensor kits are very expensive and this one failed for no apparent reason. It’s mounted dry, has remained bone dry, zero corrosion etc. and I have no way to test it nor to even get it repaired. hard to tell a customer whose vintage Data Marine stuff that lasted 31 years that his few year old very expensive Airmar ultrasonic speed unit is dead.
Obviously I will need to replace it but with what? These new units are not yet proven. If I go to a new unit it will mean a new display too $$$$ as the new ultrasonic units apparently do not send an analog pulse like the CS4500 could..
Frustrating to say the least.
-RC
Always good to hear from you, RC, though what you describe is depressing. I’m hopeful that that “new” UDST/UST transducers and processing boxes are well developed at this point, but some aspects remain mysterious and only time will indicate their reliability.
For instance, it’s still unclear to me what sort of calibration is possible, and what devices will be able to do it. The Maretron DST110 (sourced from Airmar) that I pulled to try out the UDST800 could be calibrated against SOG and even though it uses a paddlewheel I was able to get a good match between STW and SOG in zero current conditions, and hence fairly good Set/Drift calculations.
Also I noticed that the Raymarine i70s appears to have multi-point speed calibration for smart speed sensors, as shown in this entry:
https://panbo.com/archives/2016/07/good_instrument_news_garmin_gwind_wireless_2_and_raymarine_i70s.html
I just updated the DX900+ section of this entry to reflect the fact that Jeremy Anwyl’s had been bottom painted, which definitely affects performance and is therefore prohibited in the installation instructions. He will be testing a fresh DX and also a UDST800 (which can be painted).
Just sent a DX900+ to a client for a new BB&G H5000 install. And as we’ve done on every system for the past decade that requested a sonic sensor, suggested they install an analog paddlehweel prewired into the system for rapid swap if (“when” might be more accurate) the sonic unit fails. I’m optimistic for the DX but history indicates having a backup readily in place is a good move.
Not to add to any confusion, but the bottom paint I applied to the DX900+ is water based and was allowed. (At least according to the owner’s guide I have.) I think Airmar may be updating the manual to state that no bottom paint of any kind should be used, but not sure about this.
As for the UDST800, I tried one this morning and in brief sea trials can say it looks very encouraging.
Hi All, We have two DX900+ units on our 60′ cat and we will be testing them against the ST200’s also installed over the next two regattas in the Caribbean in the next 3 weeks. Any tips you can give me about what to look for. My plan is to use the ST200s into our H5000 to start with and log the data from N2K into Expedition at the same time and compare. I have not calibrated the 900s as yet, in case you have any tips.
thanks,
Larry Rosenfeld
LarryR, looking forward to hearing your results. No specific guidance to offer on testing.
Ben, do you know if UDST is (like DX900) dual-axis speed-to-water system or not. European dealer is not able to confirm this.
Sorry but that’s a no, Peter. The UDST outputs the standard set of Depth, Speed through Water, and water Temperature values. By contrast, the DX900 also measures transverse speed, calculates leeway direction, and more. That’s why it sort of needs the Bluetooth app seen up in the entry, at least until some marine instruments learn to display those values:
https://panbo.com/assets_c/2018/02/AirmarCast_app_screens_with_DX900%2B_aPanbo-16131.html
Thank you Ben for information.
I have noticed PGN 128000 issue already. Also dual-axis STW seems to be a problem for N2K-based MFDs.
Has anyone actually gotten their hands on the UDST? My Airmar DST110 paddlewheel has stopped working again, likely due to junk growing on it, and I would love to know if the UDST actually is something a sailboat should/could use.
Seconded! Doesn’t appear to be for sale yet at any of the usual suspects, and Google just returns a link to this article and not much else…
The word from Airmar: “As far as the UDST800, we have been shipping some but they already have a home when we ship them. UDST production is ramping up to a higher level in the next two weeks. ”
Also, if you have an installer/dealer with a Gemeco account, he or she can probably get one faster than you’ll see them show up in retail channels.
Anyone know if the UDST800 can be mounted inside a fibreglass hull as you could do with many depth sounders? (temperature may be off, but I would expect depth to work… not sure about speed…)
I installed a dx900 in the boat this year. The first one would not transmit depth or temp over the n2k network, but using the app I could see that the transducer was measuring these items, along with leeway, heel, trim etc. Airmar sent a new one to me and everything was transmitted via the network. The problem now is that my speed readings are wildly inaccurate. Yesterday I was tied to a dock on the Piscataqua river and it was reading the current from .8kts up to 5kts. Once underway against the current for the trip home, the Speedo cycled from under a knot to over 9kts. Not only was this clearly wrong, but as my friend who was with me pointed out, had the water speed been changing in that fashion, as quickly as it was, we wouldn’t have been able to stand on the deck without holding on tight to something.
Not sure what the issue is yet, as I haven’t had a chance to call Airmar.
Re DX900+
Interesting … ‘do not anti-foul the transponder face’. :facepalm:
However … this product seems pretty clearly targeted at (and priced accordingly) the ‘serious’ racers. Serious racers lift their boats and clean, even sand, their hulls before every race … so in the racing season … there wouldn’t be much opportunity for the transponder to foul up.
Anyway … it comes with a nice flappy-valve gizmo to make withdrawing the transponder at sea easy. So just pull it out … replace with the blanking plug … then clean it … after every time you use the boat. There replace it next time you want to use it.
If you are using the boat continuously, e.g. cruising, just make it a daily ritual to pull, clean, replace.
So I don’t see the ‘do not anti-foul the transponder face’ edict as much of an issue, really. :thumb:
The reports of widely variable readings is more of a concern. :banghead: Those same ‘serious’ racers would not take kindly to paying that much for something that is unreliable. The sooner Airmar sort out this issue … the better.
I’ve been awaiting a report on the UDST that arrived on Gizmo. It’s a revolutionary product if it actually owns up to it’s claims. It’s been a while since the review and the product is shipping and is stocked well. I’m about to pull the trigger on this one. There is a real scarcity of real world info re. this transducer on the web. So far Panbo is the only one that has a report on this. I’m a full time cruising sailor and the idea of not having to think about a paddlewheel -ever again is one that is worth the cost of this transducer. But is it still beta ware?
Hi Robert, I’m sorry to report that my UDST testing is still unresolved. The problem I’ve experienced — consistent and proportional high readings — may be due to the transducer but is much more likely the result of the installation.
When I briefly hauled Gizmo very soon after leaving her winter berth, I noticed that the UDST face was set back about 1/4-inch from flush with the casing’s outer end. The casing is about 20 years old and originally housed a Datamarine sensor, but I believe it to be standard Airmar so I let it go until I started to see apparent high readings in areas where STW should have been very close to SOG. I did fiddle with the UDST’s fixing ring so it would sit deeper in the casing — some wet fun with the boat in the water — but saw no improvement and I have not yet hauled the boat again. (I was planning to about now, but recently decided on another winter afloat partially so that I can continue other testing.)
What I should have done, and will now, is to ask Airmar for guidance. So thanks for the motivation and sorry to play an old guy who has accumulated far too much stuff to test quickly or efficiently. By the way, the UDST has performed fine in every other way, and I suspect that if I could calibrate it, even simply with a single percent type correction, it would be spot on. And I have lots of logged NMEA 2000 data logs might support that theory, though I have not looked at them yet 😉
Well, I’m still trying to get it working properly. Calibrating the transducer is a bit of a black art, and I was never able to get stAble speed readings. Depth, temperature and heel angle have been fine. I will continue to work with it next season, but if I can’t get it sorted, then I’ll go back to a paddle wheel.
Hi Eliboat, I believe from your June comment that you have DX900, not the UDST that Robert Settle just asked about. I’m sure I’m not the only who would like to hear more about your experience when possible, but the two transducers have gotten a little mixed up in this thread though they are very different.
Whoops! My bad. Yes two different technologies.
I tracked down and installed a UDST recently. Boat is still on the hard and will be until Spring, so cannot comment yet on calibration or other issues. However, I noticed that even using the casing provided by Airmar with the new transducer, I too have the same 1/4 inch gap between the face of the transducer and the outer edge of the casing.
Would prefer not to have to change out the casing again if there is another solution to get it flush (assuming that is indeed the cause of the speed issues noted above)!
Thanks so much for speaking up, Keefer, though your experience may indicate that I made a wrong assumption about the transducer fit being the problem. I have already written to Airmar and also found this in the Ultrasonic Processor manual (which was updated since my install):
“If the speed reading is consistently the same percentage higher
or lower than the true speed, the speed function within the
instrument needs to be re-calibrated. Follow the instructions in
your instrument owner’s manual.”
I’d rather calibrate the processor itself so that all instruments (and other devices that can use or display STW) would get the same data, but there may well be instruments that can apply a percentage correction that shows on their screens and maybe within their brand network. Maybe someone has a suggestion (and I will try to check out myself). Offhand, I recall that some Simrad, B&G and Furuno displays can apply corrections to some common N2K values.
Cool: Sounds like my UST800 testing issue is simply about calibration and that several options are in the works:
“Here’s where we are in this product as it pertains to calibration. As you know, our OEM partners have a long integration period to incorporate the products into their system. Once that is done, users will have a quick way to do multipoint calibrations on the UDST and DX products through their on board electronics. In much shorter time than that, we are in the final test stages for a new bit of PC software which will allow for those products and any other Smartsensor to quickly and easily be calibrated. Those calibrations will be stored in the device and will push corrected data to the network/instruments. I’m being told that it will be ready by years’ end. ”
Note that this applies to the DX transducer too, but also that my Airmar contact joked about how their developers did not specify which “years’ end” 😉
So it will be as simple as linking a PC running this software into the N2K network? My new system will have a USB-enabled XB-6000 AIS transponder that I gather ports N2K data to a PC. But will this be capable of routing the signal in the other direction, going from PC to UDST? Or will I need a different sort of link?
Sorry, Keefer, but it probably won’t be that easy. The ability of your Vesper Smart AIS to put more data than AIS out over USB and WiFi is great, but it’s limited to common navigation fields because translation is involved. This software will likely require a full-on PC-to-N2K gateway like the Airmar U200, though the Actisense NGT-1 may also work.
But I’m not sure you should worry about calibration until you try your install. I don’t think that my boat hull or the location of the UDST are weird, but it is one of the first units off the production line, I think.
Thanks Ben, much appreciated. Nothing’s ever quite so simple as we might hope it to be, eh? I will post an update re: need for calibration (or lack thereof) once the boat is wet and the system is up and running…
Thanks Ben and Keefer for your input from real-world use. Hmmm. So even with the provided Airmar housing installed the instrument face is not sitting flush with the hull? I would assume this is a major problem with the ultrasonic sensor. Water flow needs to be across the face and sitting short it would create a burble on the sensor face and create inacuracies I would assume. Unrelated Anecdotal evidence about Airmar from a fellow cruiser here in the Sea of Cortez -he says he has had 2 failures of the dst800 and now keeps a spare “just in case”…
Regardless I see myself buying the WS300 and the UDST800 and just crossing my fingers. I will haul soon and hope I can “McGuyver” any issues with the installation of the housing and sensor flush with the hull. My current location for my paddlewheel is in front of the keel (Norseman 447) and accessing it from inside requires tossing the forepeak, removing a shelf, two drawers, and a floor panel. My issue with paddlewheels is they go innacurate quite quickly after cleaning. Just a couple days. First is a slime layer quickly followed by hard growth. So they are basically useless unless maintained weekly. Who needs innacurate data? For me it’s unthinkable to toss the forepeak every time I want good speed data which is always. I have a B&G Zeus3 and heading sensor w/4G Radar -good speed data will make the whole system work with their sailing software.
So what is the consensus? Do I buy a UDST800 with some confidence? I am a typical cruiser / racer.
Well, as discussed in the November comments above, the UDST800 I’m testing is consistent and reliable, but I’m really looking forward to a means of calibrating the readings that is supposedly in the works.
Ben
I have been watching this conversation with interest. We sail in an area with strong tidal flow – and picking your time and exposure can be quite critical.
I went through the misery of trying to adapt a late model Garmin GST43 transducer to a Raymarine N2k system – ended up being an expensive (time and parts) nightmare – that ultimately didn’t work or couldn’t be properly calibrated. Nice try = no cigar.
has there been any further developments – or are we still in a state of limbo with Airmar – promising, promising but yet to deliver?
Hi Ian, I contacted Airmar and progress is being made. They have a PC program that works alongside their WeatherCaster software and can “find a DST800/UDST800/DX900 connected to the network and allow speed calibration, depth offset, depth calibration, temperature offset, and output filtering to be programmed and saved to the sensor.”
That means an Airmar or Actisense NGT-1 PC-to-NMEA 2000 bridge is needed to run the software, but I hope to try it soon. Also, it’s not yet available to the public, though apparently it is being distributed by Gemeco to technical dealers.
The calibration will also be added to Airmar’s CAST app eventually, but that’s only relevant to DX900 owners as it includes a Bluetooth radio.
Thanks Ben
I watch with interest – I am a little amazed with Airmar – their marketing hype isnt even close to matching what is out in the market. My tech guy ( a first principles devotee) is also a little bemused at marketing get ahead of the actual product promised performance. the read on the situation is its still pretty much a beta product for recreational yachties/ boaties.
I now have the boat in the water and have fired up the electronics. The UDST 800 gave me a depth reading of 3.5 feet (from the top of the keel where the thru hull is), and I measured 5.5 feet via lead line. Boat draws about 5 even and the keel is roughly 3 – 3.5 of that, so it is already pretty close without any calibration. Assuming readings stay consistent I will likely set an offset via the instruments and call it good enough. Have not had a chance to leave the slip and test out speed yet. Will report back again when we get out on the water.
After a completely lost season (engine issues), we finally got out on the water today for the first actual test of the instruments. Happy to report that the UDST 800 worked perfectly. Read 4.8 feet in the slip today, which is almost exactly what I would expect a true reading to be from the position of the transducer with no offset. While motoring around Rockhold Creek and Herring Bay on the Chesapeake, depth readings aligned with expectations for the waters we traversed, and speed through the water matched up reasonably well with SOG from the GPS (no way to judge current, but winds were calm and seas flat).
I gather from the foregoing that the Airmar UST800 is still not ready for prime time. Raymarine says that the unit will pass data to a Raymarine display, but at the moment, there is no way to calibrate. I’m curious to know how it might do in a situation like mine – a brown water, tidal creek infested area, like South Carolina. Any thoughts, observations?
As best I know, no third party display can yet directly calibrate a UST800/850 or UDST800. Some may be able to apply corrections to the output, but that’s not the same thing. Also, judging from Airmar’s download page, the calibration possible via WeatherCaster is not available to the public:
http://www.airmar.com/software-downloads.html
I will ask about this at METS.
When I go to the software download link you provided, I did not see any restriction about calibration for WeatherCaster?
Also, did you get a chance to ask at METS? Thanks,
Hi Maddox, as I commented about last April, WeatherCaster apparently needs a patch program in order to calibrate a UDST800. And that patch does not yet seem to available to the public.
However, I failed to make contact with Airmar at METS and have been poor at following up on this issue overall. I apologize, and am putting it at the top of my list.
I have the DST800 and would like to use the UDST800. Does the UDST800 use the same housing as the DST800 or do I have to haul and replace/install a new housing?
Yes, they both use the common 617V casing, either P, B, or SS depending on material they’re made from:
http://www.airmar.com/guides.html?cat=nmea
If the casing is to be left in place, switching only the transducer itself, is there a difference between P, B, or SS units beyond pricing that might be dictated by the casing we won’t use? Will a P transducer be okay in the SS through hull.?
So now her we are May 2020 and I have just installed the UDST800 on my Jeanneau sailboat. So far it performs very well but with a fully updated Raymarine i70s it cannot be calibrated. I contacted Raymarine Australia and they know of no plans to add this support. SO is there another way or can we get Raymarine to work on this?
Leslie, I just emailed Airmar asking if there had been any progress either at getting companies like Raymarine to support UDST calibration or to at least make user calibration possible with a PC and NMEA 2000 gateway. Note that there is way to do the latter, but a year ago it was only available to dealer/installers via Gemeco (and other Airmar distributors I presume).
This is a discouraging situation, especially since Airmar just introduced the DST810 with what looks to be excellent calibration and other benefits via its built-in Bluetooth and the CAST app:
https://panbo.com/calibrate-speed-receive-data-wirelessly-new-airmar-dst810/
Unfortunately the Ultrasonic Processor box does not have Bluetooth built in (yet).
I contacted Gemeco (Airmar’s dealer only the US) in January of this year (2020) and a technician replied with a link to the necessary software to add to Weathercaster app that allows calibration. It requires either an Actisense NGT-1-USB or the Airmar U200 NMEA gateway to provide NMEA 2000 write capability. I purchased the Actisense, which is not inexpensive, but provides other monitoring as well. The program is not very intuative to us, but I managed quite well and set an offset in the UDST-800 and that has been working well.
Thank you Maddox, I will order the Actisense NGT-1-USB from the local Australian dealer. Could you send me the link to software to add to the Weathercaster app to allow calibration?
Leslie – I sent Ben a copy of the email I got that has a link to the software and instructions on use hoping he can pass it on to your email address.
Well, nice to see that Gemeco gave Maddox a link to the calibration software though he’s apparently not a regular pro customer and bought his UDST-800 elsewhere. And VERY NICE that Maddox sent the email conversation and configuration app link to Leslie via Panbo (yes, that works because we can see the email addresses of registered readers).
One sentence I noticed in Gemeco’s 1/2020 email was “be aware that the linked software is still in Beta and can be a bit buggy, but works well in most instances.” So be aware, Leslie, and that may explain why the app still isn’t available an Airmar’s software download page.
I just read an article in Marine Technology News where they describe how the DX900+ was originally developed by the Subsidiary, Marport, for Fishing Nets! Then they decided that it would be a great fit for Sailboats. Go Figure. I am finishing up my second season with this device, and it has finally calmed down and started working. The Depth has always worked beautifully, much more reliable than previous ultrasonics. It does not seem to be deceived by mud and weeds. The speed is finally working OK, and the temperature is a work in progress. I currently have it at -3 F, which seems pretty good. I seem to have to do the offset on my Zeus3, tho. The heel and pitch show up on there as well, but I just changed that to the Precision 9 Compass.
I have not read the above comments and looking for any clarification to what be wrong with my system (I’m already in contact with Airmar, but this post to find inspirations in what to look for in troubleshooting).
I had to begin with a SDST800 (Standard paddlewheel), but heard about the DX-900+ and got one because of leeway, 10Hz update rate and good speed under 15-20 degrees heel. That one I newer got stable readings out of. Send it back to check at Airmar, and the took it back under warranty and said that it was not suitable for my boat.
I when got the UDST-800 recemented (Not directly from Airmar, but for a dealer) telling me the only thing I will not get was leeway, and since paddlewheels sucks under heel conditions, I decided to try the UDST-800.
The first one (have now treid 2) I got worked quite OK for 2 months, I had to set a 2 second filter in my Sailmon race computer to get stable readings out, BUT a lot better than DX-900+.
Then it started to fall to 0 kn when sailing (any speed made it happened). That was traced back to a unreliable NMEA2000 power supply.
But now the speed jumps +/- 0.5 kn of SOG or more random. The suspension now goes to that 1m in front of the UDST-800 I have a retractable bow thruster (https://side-power.com/produkt/19097/srv100-vertical-retract-12v/) possibility that cavitation relating to the gap in the plate on that one. Any good inputs?
Does the UST800 output the distance log PGN 128275?
Hi Chuck, All certified NMEA 2000 devices are supposed to include a printed list of supported PGNs, usually found at the back of the manual. I can’t find this list for the UST800 but note the screens at the end of the entry above, showing a very similar UDST800 outputting “Water Distance.” I think that’s what you’re looking for, but you might want to doublecheck with Airmar or Gemeco.
Yes – the UDST800 does output distance log. Here is the list of pgns it is currently producing on our boat:
PGN
126464:
126996
126998
128259:
128267:
128275:
130311:
Thank you both, Ben and Maddox!
This thread has been really really helpful – thanks for putting all this information together in one place.
I installed a UST800 at the end of boating season 2020, and now have a need to calibrate it. My symptoms are very similar to Ben’s – speed readings are reliably offset by the same percentage.
I contacted Airmar for support, and they told me that calibration had to be completed through the display units. In this case Raymarine – which doesn’t appear supported.
Just wondering if there are any known updates on this front, or if the weathercaster software with UST calibration is now a public offering? It would be preferred (and probably my only option) to make calibration changes directly to the ultrasonic processor.
If not – can anyone point me in the direction of a beta-download. I am tech oriented, and would take my chances with buggy software at this point.
It’s really disappointing that there isn’t better support for a product this expensive.
Thanks in advance
Hi Erock,
I just emailed the info Maddox discussed above, and the Dropbox files still seem to be there.
Good luck with calibration!
I have the DX900+ and also discovered that trying to calibrate using the Bluetooth app was an exercise in Futility. I have had good luck calibrating it with the Zeus3. The depth is spot on, the water temp has calmed down to only needing a few degrees adjustment, and the speed – is usually good. Initially, it was a little crazy, but it has also calmed down. Interesting to hear that the Raymarine won’t work with it. One of the few comments that made me feel better about sticking with B&G.
Hi Bill, It’s great that your B&G displays are now more accurate, but I think you’ll find that the calibration is being done within the B&G system, not in the DX900+. You can tell if you see uncalibrated readings on a non B&G display or via a gateway that shows the DX output. Navico and Furuno often offer this sort of generic calibration, while Garmin and Raymarine seem more focused on direct calibrating their own sensors, and sometimes other sensor brands like Airmar. Here’s some detail about what a Ray i70s can do with a regular Airmar Smart speed sensor:
https://panbo.com/good-instrument-news-garmin-gwind-wireless-2-and-raymarine-i70s/
Yes, it is being calibrated through B&G – Sorry, I guess I wasn’t clear on that. By Bluetooth, I meant the Airmar Cast App. Just looking for it, I notice that I never put it on my new phone, so I guess I have pretty much given up on it. I originally thought it would be better to be corrected at the source with the Airmar software, but that didn’t work, so I gave up on it and used the B&G. I can’t see myself screwing around with the Cast app to look for leeway either, so I hope B&G will at some point handle it. It seems toward the end of the 2020 season I noticed something on the Zeus mentioning leeway, but I can’t find anything on it in the Manual. However, on Page 82 of the H5000 CPU manual, there is a mention of leeway, configure and setup, on the Webserver pages, which I haven’t even gotten into. I don’t know if this means that The Zeus will actually use the leeway feature of the DX900+ or not. I should also say, that when all the instruments started to coalesce last summer, it was when I installed the H5000 CPU, and got rid of all things 0183, like older converters, etc.
Might someone be willing to capture the network traffic while calibrating the instrument and share the capture with me? I am hoping to decipher the calibration messages and add them to the canboat PGN database.
I had a good experience with the CS4500, the UST800’s predecessor that provided an analog pulse output until I expected more from it. No need to clean was appreciated, but when I started to race the boat seriously I came to realize the reported speed values jump around quite a bit after capturing the NMEA0183 values to the computer. A replacement did the same. There was a frequent variation of 0.5 knots between captured values and occasional discrepancies of 1.2 knots or more (while traveling at 6 knots in a sailboat). At high damping values, minute to minute, different speeds were reported +/- 0.3 knots even though the boats GPS speed over ground was basically constant. Not ideal for providing the sailor feedback about differences in sail trim. It turned out better to race with a standard sensor and clean it frequently.
I look forward to the DX-900+, which is based on entirely different technology and the capability to measure leeway, when I hear the all clear on Panbo that it is being successfully used.
Good to hear from you, Dan, and also happy to report that Kees told me in early December that Airmar was shipping him a DX900+ “that is apparently (more) suited to a bigger/metal boat.” He and Merrimac are afloat in the Caribbean, so his long-planned review may happen fairly soon.
All – Thanks!
I was able to download the software. Just as an FYI, I did email airmar support, and they eventually also offered the link.
I’ll be trying out the process soon, and will report back my experience.
Thanks again!
I have since received the improved DX900+ and the noise is fully gone. We run a hefty 25+ node NMEA2000 network with permanent DC/DC charger, and the hull section where the DX900+ lives is 15 mm of aluminium. So I think I can say that this version fixes the noise problems.
Like others, I’m still struggling with calibration, when I go at a particular speed and calibrate it seems off again at a different speed. According to Airmar the sensing mechanism itself is totally linear, so this might be caused by the installation housing.
To be continued…
I tried a DX900 + (installed at the end of the 2019 season) ended up sending it back. Have now tried 2 different UDST800 all 3 units (2 pcs udst800 and 1 dx900 +) with the same problem speed jump +/- 0.5 knots, and DX900 + jumped in speed while the boat was in port. Kees is it a new version DX900 +? I have a Sailmon race computer (B&G H5000 competitor) so calibration is not a problem. my problem is getting the right speed when the boat heels. i have been offered a dst810 in exchange but it is just a paddle and does not solve my problem. therefore I am very curious if there is a new dx900 + on the way…
Hi Tue,
I received new hardware, both a new sensor (with label “ground isolated”) and a new black box. As of now I don’t know Airmar’s plans yet, but I will.
Any update on the speed calibration Kees?
I’m keen to get the DX900+ and I plan to take the NMEA183 version to avoid the processor box.
However, with all the issues described on this site, I’m having second thoughts.
I’m not impressed with Airmar – my 3rd ST800 just quit working after little more than 2 years and everyone I know have lost the temperture reading due to the burnt thermistor.
Unfortunately I have not been able to find an alternative.
I am getting the sense that some calibration issues with the UDST and others might be an installation/RFI problem. It’s not practical/impossible to isolate from other wiring runs and stray induced currents could be a real issue. Looks like Airmar has introduced an updated unit with “discreet” grounds
I did several test run where only battery, nmea2000 logger, gps and sensor installed. nothing Else connected and Wire Placed close to battery and sensor. Stil jumping in speed
Thanks for all the useful info above. I am very interested in getting a depth/speed/temp transducer without a paddle wheel and I was very interested in getting the 128000 Leeway PGN, but reading all this has frankly put me off buying the Airmar DX900+ or UDST800 as it seems as though these products are still in their infancy.
Is this a reasonable conclusion? I am a cruiser, not a racer, so I value reliability. Are there any alternative brands that have better reliability? Thanks, Hamish
My experience with a recent install of the UDST is wonderful. I live aboard and sail fulltime -currently in the Sea of Cortez in Mexico. The UDST in combination with the Sense-9 heading sensor, a Zeus3 MFD, Triton display and B&G Wireless Wind is working as advertised. I never had to configure or select devices. They all just sensed each other and seamlessly accessed the correct page-ins. The UDST feeds the system with info to display current and current speed very accurately. That is remarkable! That has proved to be very useful in the north here where tides can reach 22 feet. The UDST gives me depth to about 300 feet or so and seems to be very accurate in shallow water. The temp sensor is spot on and needing no calibration. My only wish would be to somehow power up the NMEA network selectively without activating all devices. When at anchor I like to see windspeed via my Triton display which also requires all other NMEA devices on the network to power on ie. heading sensor and the UDST. I am 100% solar when voyaging.
Hi Robert,
Have you thought about using a NMEA 2000 Split Power Tee? These devices plug in-line to the NMEA backbone just like a regular drop tee, but have two power inputs. Each power input will power the bus connected to each side of the power tee independently. The data pins run straight through the power tee so the backbone bus stays intact. You could then put any devices that should be powered up by the first breaker on one side of the tee (Wind sensor and Triton), and the devices you want turned on by the second breaker on the other side of the tee (everything else).
As suggested by Joseph you can split your N2K backbone into segments with individual power.
The Power T is a slick way to do this, but the quick-n-dirty way is to simply cut the red wire in the drop cable to your Triton and give it its own power.
I split my backbone this way for much the same reason you describe and it works like a charm.
After about 3 years of the DX900+, I can say I wish I had just gotten the ultrasonic. (Altho from reading above, I may then be bitching about that!) The temperature was initially crazy, but over the last year or so has settled down, and seems correct. The Depth is the star, I can say I believe this electromagnetic technology it is better than any other technology I have used. Where is shines, is in weeds, muck, or other uncertain bottoms, as it seems to shoot right through all that and give accurate readings. Best of all, it is on all the time. Which leads me to the speed. It will only report for a couple hours, sometimes the whole day, but never to the time I turn it on next. Temp and Depth are always there. What works best is if I unscrew the the Nk2 connection, then reconnect, it pops back up. But it will never follow through from one power cycle to the next. Which means I need a new transducer. Not happy with this one. I am curious if they will swap me out with the ‘New and improved Isolated Ground”
Hello,
I recently bought a CS4500. I sail on relatively shallow freshwater, in southern Brazil.
The unit works wonderfully anywhere deeper than 10 feet.
However, when it’s shallower than that (a lot of my sailing time), the readings go crazy, fluctuating around 1.5-2kts around the correct figure, in cycles.
Has anyone had any experience similar to mine, i.e. a malfunction of CS4500 because of the water being shallow?
I installed a DX900+ and fared it so that when installed the bottom absolutely smooth. Like many, I had great hopes because when pulling my old transducer, water would “fountain” into my salon and make a mess. Well, long story short, the DX900+ resolved the issue of fountaining water. As long as you keep the fouling to a reasonable level, the transducer is easy enough to wipe clean with a rag while cleaning the bottom. But sadly, the darn thing isn’t very accurate either for speed or depth. The calibration tool is worthless because the sensor is so inaccurate. It’s really too bad… It’s a grand concept. But even if I returned it, I wouldn’t be remotely compensated for the thousands I spent hauling, epoxying and faring the through-hull. Save your money until the next improvement, and then test before trying to perfect your installation.
Hi. Greetings from the UK. I had a CS4500 on a previous boat for several years, which performed faultlessly, and saved constantly having to lift and clean the paddlewheel and bail out the bilge. I bought a new boat in 2018, and eventually got around to fitting a UDST800 as the latest technology from Airmar. Had the same calibration issues as others have reported, but got hold of the beta software from Gemeco which was clunky but did the job. However the UDST800 totally failed last year, and I eventually got an RMA from Airmar EMEA in France and sent back the unit. They promised a replacement, but to cut a long story short, I still haven’t received one after nearly a year. Many, many broken promises. No-one in UK holds any stock of these, and i don’t believe the lead times they quote. Are these products still in production in USA, and are they proving to be reliable now? Any feedback would be useful!
Hi Peter, Airmar US distributor Gemeco show “out of stock” but with expected availability in about a month:
https://www.gemeco.com/Product/UDST800P-N2
Apparently they suffered severe supply chain issues last year, more on that here:
https://www.p2marine.com/airmar-transducer-availability
Hello Peter, sorry to hear about your transducer dying. My UST800 (no depth) is still functioning after two years. Do you have any more info on the calibration software? I’ve been wanting to calibrate mine for ages. Thank you.
My UDST800 is still going strong after four years and many many sea miles. Speed reading is consistently a little higher than would be expected from SOG/current differential, but unlike a paddle wheel it always reads, even with some growth on it. Depth and temp are very reliable. I have learned to live with the speed issue rather than trying to go through the trouble of calibration as described above.
I agree with everything you say. My UDST8000 is going strong after 2 years. I just have to accept that it is not supported by Raymarine. This means it cant be calibrated by the plotter and that I cant apply a depth offset.
Thanks guys for your input. Gives me a little more confidence in what I am being told by Airmar. And also some reassurance that the product is solid. Latest delivery promise is next week – still keeping fingers crossed!
Here’s the link to the Beta Cal software I got from Gemeco. Still seems to be valid.
https://www.dropbox.com/sh/0kvv9ilh8qed4ig/AAAdeK81d_J0_3aCLbX1t2w4a?dl=0
I used an Actisense NGT-1-USB to connect my laptop to the N2K network.
Thank you for the link Peter! I’ll give it a try next time I have access to a Windows system. Good luck with your replacement transducer. Let us know how it goes…
I think that characterizing the paddleless Airmar as “solid” is a stretch. It is not accurate for speed or depth, nor does the calibration software correct the issues. Basically I would use the speed as a reference number … I’d use GPS speed where there was no current, then use the calibration tool, then when we’d race, I’d used the speedo as “I”m going faster” or “I’m going slower”. That’s about all you can get from it. Depth would usually just stay on one number unless there was a big change in depth. However, we were pretty obsessive about keeping the boat clean, so not having to pull the transducer at the end of the weekend was great. The diver or I could keep the transducer clean, just by wiping it with a rag as long as we didn’t let it build up.
I’ve had two (2) DST800s with mechanical paddle wheels and they both have easily clogged up despite periodic bottom cleaning and AF paint.
I’m curious how reliable this new UDST will be over longer time periods.
Started out loving my UDST800 but have had lots of problems with it. RC’s post at the top of the comments is exactly what we found as far as troubleshooting.
The boat speed goes to zero randomly. May stay there for minutes or hours. Nothing can be done in the field and we are in the Tuamotus so returning it for service is not easy. We finally put in our old DST800 and will try to get it back to Airmar next year. You can read more about my experience as well as another UDST owner who had the exact same problem on Cruisers Forum:
https://www.cruisersforum.com/forums/f13/experience-w-airmar-ultrasonic-sensor-udst800-204454.html
It is a really cool product if it would work and, despite some of the bad news I’ve read, I want to be hopeful that Airmar can fix it.
It is now 18 months since I returned my UDST800 under warranty. Despite many promises, I have still not received a replacement. Airmar EMEA always say they are hoping for new deliveries soon, and mine is a priority. Does anyone know if Airmar is back in production with this product? Have they admitted that there are deisgn problems, or are they still saying the delays are down to sourcing components?
Hi Peter,
My wife just flew to the US to visit her mother and brought our USDT800 with her. She mailed it back last week and they just contacted me that they are sending a replacement. So fingers crossed.
Cheers,
Bruce
Bruce I hope that works and it will be interesting to hear your experience. On our side we’ve decided to just keep our DST800 and clean it periodically knowing this will not really fix it. Secondly, we ordered and just received a new sounder GT23M-TH. It will be installed next to the DST and will be a backup for accurate depth readings as well as it will provide downward ClearVU at the times when we want a better survey of an anchorage.
I think I’m resigned to the fact that we cannot count on a reliable water speed sensor at this time.
I’ve now received a brand new replacement UDST800. Boat goes in the water next week, so fingers crossed! Will report back after sea trials.
Hi All,
My wife received the replacement UDST800 within 2 weeks of shipping back the old one. That was good news as she was able to bring it home with her. We replaced the DST800 we were using and *so far* the UDST seems to be working fine. We sailed from the Marquesas to the Tuamotus (about 500 miles total) and no problems. Fingers crossed. I’ll post if anything goes wrong.
Cheers,
Bruce
My replacement UDST800 lasted a few weeks, and less than 100 miles before the speed suddenly went to zero. Up until then it was looking quite accurate without calibration. Depth was still operational. Luckily I left my old paddlewheel triducer ready to swap back. I’ve just about given up now. Resigned to mopping out the bilge at the start and end of each trip to keep the wheel turning. I’m afraid I cannot recommend this product, or Airmar’s after sales service! Peter
Hi Peter,
Sorry to hear that news. I’ll hope ours does better than that. Really a shame because it seems like a great project if it would just continue to work.
Cheers,
Bruce
Just adding my two cents. I had the CS4500 on my previous sailboat, and it worked very well for maybe three years, then stopped. Airmar’s support had me do some tests on the external electronics, determined the problem was in the sensor and, since it was all potted, there was no way to repair it. Ever the optimist, I bought the UDST800 for my next boat. It initially worked fine, although I had to buy a Garmin MFD to calibrate the depth. Neither of my Raymarine units would do that, although they saw the Airmar just fine. Airmar said only the Garmin GMI 10 was certified to calibrate the 800. They corrected that to the GMI 20, when I informed them the 10 was no longer in production. (BTW I really like the GPS odometer screen on the GMI 20 – I just took my first big trip, to the Bahamas, and that feature was helpful and fun). Anyhow, the UDST800 fairly quickly stopped showing anything but zero for speed. I’d bought it some time ago, so there’s no longer a warranty. Now I’m hoping I can find something else that will fit in what I think is its somewhat oversized thru hull. I’m not keen on having it be another Airmar product, as I find both reliability and support to be major issues.
I know this thread is pretty old, but I’d like to add to it. I had purchased a CS4500 over ten years ago and it sat in storage until June 2022, as we calibrated instruments for the 2022 PacCup. We have the CS2400 and a standard paddle wheel. To switch between we swap transducer in the hole and swap cable connections using a standard 5-pin automotive connector. This jumper feeds the speed input to a RayMarine ITC-5 analog-to-digital converter.
We were able to successfully calibrate the CS4500 using the ITC-5. It was very linear. It seems to work well for about a year. Then as we were getting ready to rely on it for polar performance measurements, it quite working and we swapped back to the paddle-wheel.
I had high-hopes for this technology, but reading all of the posts here, it sounds like Airmar has still not figured out how to make it reliable, including the newer version that connects directly to the NK2000 network.
If anyone has any more recent experiences to share, I’d sure like to hear it. I did notice that Airmar is now offering a new paddle-wheel technology. Does this mean that they have given up on ultrasonic and EM transducers?
Cheers,
Mark
Sorry for typo in that last entry CS2400 >>>> CS4500.
I passed on the UDST800 years back due to the reported reliability issues. A local dealer is telling me those have been resolved and the new version of this device are much better. Any real world data out there to suggest these things are now reliable?
Not quite answering the question, but since I got an email reminding me of this thread… I have now been using my UDST800 for about 5 years and have found it quite reliable. I hope they have by now addressed the calibration issue, but for me the only thing I use boat speed for is as a comparison to GPS speed to get a sense of what current might be doing. So as long as the instrument is consistent, absolute precision doesn’t really matter. I realize there are many folks out there for whom that is not good enough! Bottom line is that even the imperfect first generation was and is far superior to a paddle wheel, at least for this cruising sailor.
I need to update my earlier comment on the water speed failing on my UDST800. After that Bahamas trip, I contacted Airmar and got a pretty quick response. The tech had me try a few things. He said that I’d reported the problem just within the warranty period. IIRC, they had me send the bad unit back for testing. At any rate, they eventually sent me a new transducer, and it worked perfectly. HOWEVER, we’re just back from a two-week trip, and, while the speed and temp work fine, the depth signal became intermittent at best. I’ll pull it and see if there’s some fouling, but you’d think the speed would be out, too. The interweb consensus seems to be that Airmar quality is improving, but we’ll see. I’ll update this once I determine whether it’s just a fouling issue this time.
Similar to Keefer, I have also been using my UDST800 for about 5 years. Calibrating it was a it complex, but once done, it has been working great!
Just received my 3rd or 4th (lost count) replacement UDST800. We’ll see if this one doesn’t have the problem where the boat speed disappears for hours at a time…