... written for Panbo by Dan Corcoran and posted on Oct 5, 2009
Guest Entry by Dan Corcoran ---
Following up my earlier evaluation of the Airmar Ultrasonic Weather station here on Panbo (actually there is more to come), I have another Airmar ultrasonic product to tell you about. It's the CS4500, an ultrasonic boat speed sensor that I've been using for the past three years, and I'll be covering it in a three part series.
At first, I couldn't come up with much to write about this product, mainly because once installed, it's easy to forget. Not forgotten, however, is the painstaking monthly, if not weekly, cleaning ordeal of the venerable paddlewheel along with the resulting mess caused by exposing the inside of our boats to a temporary but explosive ingress of seawater.
Since I have not done this for three years, I had to go look up what is the state of the art for cleaning paddlewheels. I recall using a pointed scraper from my soldering kit for partial cleanings through the summer, and on sailing anarchy I found people who go as far as removing the pin to dip the paddle wheel part itself in vinegar and others that coat it with VC17 (to extend time between cleanings). DDW wrote "the best way is to scrape it clean, very carefully buff it, then store it permanently under your bed at home. That way it stays nice and clean and accurate." With the CS4500, that's history because I coat the CS4500 with anti-fouling paint at the start of the season, install before she is splashed in the spring, and remove it after she is hauled.
As illustrated in the picture below, the CS4500 uses two ultrasonic transducers to detect the movement of water without moving parts, replacing the paddlewheel sensor with a more highly accurate measurement of boat speed which is maintenance free. The ultrasonic process is necessarily different than the PB200 ultrasonic wind measurement that I reported on earlier this year. With the CS4500 there are two ultrasonic sensors, forward and aft, which use pulses to collect echoes from small particles in the passing water. The time it takes for particles to transit between the two sensors are measured and used to calculate boat speed.
I imagine the no maintenance aspect is the main benefit for power boat owners but for sailors such as myself, that's not even the best part.
On sailboats, cleaning a paddlewheel isn't nearly as much of a hassle compared to leaving the dock and then finding out it needs to be cleaned. Generally, it's too late at that point, and you're stuck with an inaccurate boat speed if there is any current under your boat, or if you have no GPS to lean on, you have no boat speed measurement at all.
Working in reverse, the number two benefit of the CS4500 is that I always have a reliable reading of boat speed. This includes reliability at very low velocities when only the most recently cleaned paddelwheels will report boat speed. It's not unusual to be tied at the dock, and see boat speeds of just 0.10 knots.
The number one benefit is the reliablility in true wind angle measurement, which I will report on in Part II of this series, made possible by an accurate boat speed measurement (CS4500) combined with an accurate apparent wind measurement (PB200). It is useful to the entire range of sailing activities such as day sailing, racing, coastal and ocean cruising.
In Part III, I will touch upon mating the CS4500 with a Raymarine ST70 speed pod and behold, the result being an even more accurate and NMEA2000 compatible STW source!
With the improvement in the accuracy of GPS, I did a comparison and found the GPS determination of speed to be more accurate. The paddle wheel and ultrasound sensors are the vector sum of current and SOG while the GPS is only SOG. I'm not sure what role the through hull sensors have with the adoption of GPS.
Even the hand held GPS units are remarkably accurate. Other thoughts from the readership?
Posted by: Keith at October 5, 2009 9:53 AM |Reply
Thanks Dan. Are you sure the 'ducer paint has no effect on the sensors?
Keith: knowing the true wind speed and direction is useful to sailors. It can be determined when you correct your wind information for the effects of current. With the level of reliablilty we are approaching, it will be possible to accurately measure crab angle too! That will take a lot of the guess-work out of beating off a lea shore.
So we need both the SOG and through the water.
Posted by: Sandy Daugherty at October 5, 2009 10:14 AM |Reply
Having both allows you to determine the effects of current. It's another tool to use.
Posted by: Stephen at October 5, 2009 10:20 AM |Reply
Does it show negative speed if you are moving backwards?
Per Sandy and Stephen, sailboats need STW to measure their performance irrespective of current, the same way we want both HDG and COG.
Dan - the paddle wheels also incorporate depth and water temp. Does the ultrasonic provide that, or did you install a separate depth / temp transducer?
Posted by: Russ at October 5, 2009 10:51 AM |Reply
Sandy, the paint is recommended in the aimar instructions.
Sandy, right on about the importance of true wind! A measurement of true wind relative to water (the wind the boat would experience if it came to a dead stop on the water, and not anchored to the ground), is the wind we would best compare our boat performance too. If we compare boat speed to apparent wind or worse, compare GPS speed over ground to apparent wind, we will just get confused and fustrated at our attempts to determine the best settings of various sail controls on our boat (e.g. headsail tension, vang, outhaul, backstay, etc.) to keep it moving fast in various wind strengths.
Stephen is right, with the caveat that the heading accuracy also needs to be very good.
Russ, my original paddlewheel did not have depth and temp, so I have always had a separate transducer for depth & temp.
Power boats can use accurate STW too, particularly if they have good fuel management gear. To truly compare how efficiently your engine(s) are burning fuel from one trip to another, you want to compare mile per gallon calculated on speed through the water, leaving current out. Lots of power boaters like to know current set and drift, too, and that requires accurate STW and heading computed against COG/SOG.
Russ, I just heard in Florida that Airmar is working on an ultrasonic STW triducer. It will have multi format STW/DPT/WT output too -- NMEA 0183, 2000, and analog. Sounds great but I have no idea what it will cost or when it will ship.
(I too would be interested to know if a CS4500 delivers speed in reverse, but it should be noted that Richard sails a multihull, which can sometimes get caught in irons ;-)
Posted by: Ben E at October 5, 2009 11:52 AM |Reply
Good article. I've been looking at the CS4500 for a while and it's nice to find a thorough review.
What would be the best (that is, cheap but reliable) way to convert the CS4500's 0183 output for use on a largely N2K network? I'd prefer to wait for the triducer Ben mentions but with no known release date...
Thanks, Dan.
Posted by: Adam at October 5, 2009 12:09 PM |Reply
Dan:
If I recall correctly you have Ray E displays.
Does the CS4500 display STW on the E?
I have a Ray DSM, I wonder if the CS4500 will overwrite the speed coming from the DSM,which is sometimes unreliable, and it's transducer.
Posted by: Bill at October 5, 2009 12:16 PM |Reply
Speed in reverse: Can't say that I ever noticed. I'll run my boat in reverse this weekend and post the result.
True wind: Opps, I am getting ahead of myself by saying anything ahead of part II.
No, I can't think of any practical use for speed in reverse. Just, as a software guy, I'm always thinking about the special case inputs that need testing.
A paddlewheel just counts a pulse frequency and can not tell the direction of travel. But with this sensor, the direction should be available, and the system designer has to decide what to do with this information. He/she could set the output to zero. Or they could discard the sign and output the absolute value (like a paddle wheel). Or output the negative number and risk breaking any display system that is not expecting input in that range.
I would probably play it safe and output the absolute value. I would not want any support calls from the idiot who installs the thing backwards!
Nah, the CS4500 can't possibly do negative speeds when the interface is the same as a paddle wheel -- e.g. pulses that are counted by the ST70 pod or directly by an instrument.
Interestingly, the announced Airmar DST-900 uses a magnetic field instead of ultrasound:
"The NEW innovative speed sensor circuitry creates a magnetic field in the water. Speed is accurately measured by the voltage created through conductive properties of water, combined with the forward motion of a vessel."
Why would Airmar choose to go to a magnetic sensor instead of ultrasonic?
Thanks for the link, Kees; I missed that one too! I think the model I heard a little about at NMEA may be different as I understood it to multi modal while the DST-900EM is just NMEA 2000. Adam, note that the "available" date is Q3 2009, which is really soon.
Posted by: Ben E at October 5, 2009 3:20 PM |Reply
NMEA-2000: While I was doing some background research I came across the DST-900EM Kees wrote about above, in an obscure portion of the website.
After speaking with Airmar I learned they decided not to introduce the product and will instead introduce a next generation CS4500 based on the �rock solid performance� of the product I evaluated here.
Airmar shared with me today that the next generation CS4500 is projected to come to market in Fall 2010.
Adam: Mentioned above is a Raymarine product that takes the output of the CS4500 and will output to NMEA-2000 now. Note, the CS4500 output is analog paddlewheel, not 0183.
Bill: Yes, I indeed did test with the Raymarine E-series, but I think in this case you can expect any product that uses an Airmar paddlewheel to accept the CS4500 as a replacement. In my case the Raymarine ST-60 Tridata does the conversion from analog paddlewheel to 0183, replacing the paddlewheel that comes with the ST60. I am not familiar with the Ray DSM.
Does anybody know why B&G stopped using the CS4500 as their ultrasonic speed sensor?
Thanks
Francisco
Posted by: Francisco at October 5, 2009 6:10 PM |Reply
I have just completed a 1500 mile cruise up the Great Lakes with the CS4500 reading through an ST70 speed pod and E-series system. The accuracy was overall pretty good, especially after some careful tweaking of the calibration parameters available in the ST70 transducer menu. It would read within 0.1-0.2 of SOG about 95% of the time when there was no known current. The ST70 has calibration factors at 2, 4, 8 knots (and above), evidently interpolation is done between them and so a bit of thought is required when deciding which one to tweak.
Because the ST70 broadcasts the speed throughout the system, it is available everywhere, including the E series displays and to the ships computer via a ST1 to Bluetooth bridge. It does not read negative in reverse, though it will read a small value (0.1 - 0.3) at anchor or tied up if there is much water movement form waves or wind or whatever. This will accumulate a mile or two overnight.
I should note that the paddlewheel that came with the ST70 pod is still remarkably clean and accurate, being still kept in shrink wrap under my bed at home.
It lists for about $556. The CS4500 costs about $700 and you need a ST70 Speedpod to convert the paddlewheel output to NMEA 2000 and then you still need depth. That's three devices, two holes, a lot of money and more power.
Posted by: Chris at October 5, 2009 8:13 PM |Reply
Thanks for the review Dan, I have been interested in the CS4500 for a few years but noticed the ST-900EM in Airmar's catalog this year and assumed that it would be an improvement over ultrasonic detection. I finally contacted Airmar on Sep 9. Their response: "Due to severe decreased market demand this year, we have completely stopped the ST-900EM development project. While we have already invested much in this project, there is still a lot with respect to tooling for production that we decided to postpone. We may decide to finish development next year, if the market picks up."
I would gladly pay $556 for a reliable paddlewheel replacement with N2K. I wonder where Chris got that price though.
I think that I saw a NKE ad saying that they would have a CS4500 instrument on display at Annapolis. I plan to check it out.
Jon
Posted by: JonM at October 5, 2009 10:07 PM |Reply
Oops, sorry for the double post. I was left at a blank page from the CGI and it looked like the post failed. Since a post I made last week never showed up I thought that I had a browser incompatibility issue.
Posted by: JonM at October 5, 2009 10:17 PM |Reply
nice article. I just wanted to make a correction to a few responses. true wind is important to a sailor, but its correct derivation would use SOG and COG. the speed of the boat through the water, as measured by a paddlewheel or this new Airmar transducer is not a contibutor to the functon. knowing your velocity relative to the wind is required, and this uses SOG/COG.
JonM, Sorry about Panbo comment crankiness. Not sure what's up, but am trying to figure it out.
Daniel, true wind relative to boat purposely does not include water motion and therefore uses STW instead of SOG/COG. True wind relative to earth, often called ground wind, does use SOG/COG.
Posted by: Ben E at October 5, 2009 10:39 PM |Reply
JonM, I googled and found that JGTech had a price of �349 and it was due very soon. But not seeing anything on the Airmar I'm inclined to agree they're postponing/canceling it.
Posted by: Chris at October 6, 2009 1:44 AM |Reply
Regarding JonM's question about CS4500 in the nke booth at Annapolis. It will not be there, nke will be showing it's own Ultrasonic sensor that has no relation to the Airmar CS4500 except to fit in the same through-hull fittings and uses a similar sensing technology. This sensor has no junction box and has three output modes, NMEA 0183, 5 or 12V pulse to mate with most other instrument systems and nke bus output.
The nke sensor is a product that has been under development in France for the last 6 years and is now used all over the world in boat speed critical applications up to and including use in the current crop of America's Cup contenders.
When B&G dropped the CS4500 sensor it was primarily due to reliability issues and the fact that at certain speeds the sensor was unstable leading to a jitter in boat speed that was unacceptable to performance oriented customers. If it worked for you it worked very well but there was a high enough percentage of problems that B&G removed it from the product mix. Bear in mind that this was over 4 years ago and the good folks at Airmar have been working on it in this time.
"If it worked for you it worked very well but there was a high enough percentage of problems that..."
Well, there's an interesting bit of real world nuance. I'll bet there are sailors walking around today who think the CS4500 is plain no good because it did not work right on some boats. We should all remember that nuance when we hear a product trashed. Thanks, Bob.
Posted by: Ben E at October 6, 2009 10:01 AM |Reply
I just got off the phone with Airmar.
The DST-900EM has been postponed mostly due to the downturn of the economy. They are working on a triducer version of the CS4500 which would be due out in 1Q 2010. They also said the DST900EM was better for high performance powerboats whereas the CS4500 was better for sailboats.
Posted by: Chris at October 6, 2009 11:58 AM |Reply
I recall there was scattered mention of user discontent with the CS4500 sold thru B&G dating before the time I purchased it, and with B&G not reselling them it made it hard for me to get.
The CS4500 I purchased (and evaluated above) in 2006 was the same hardware but with a 2005 software release that corrected the issues.
My understanding is that those earlier CS4500's can be flash upgraded at the factory (not field upgradable) for users with the earlier software release.
I wonder how much of my success also relied upon a recommendation in the manual that the CS4500 not be installed in a situation where another thru-hull would be forward of it. In my case I had a depth/temp sensor forward of my paddlewheel, so I followed the advice and installed another thru-hull for the CS4500 rather then reuse the paddlewheel thru-hull.
"Daniel, true wind relative to boat purposely does not include water motion and therefore uses STW instead of SOG/COG. True wind relative to earth, often called ground wind, does use SOG/COG." -Ben
I simply don't understand exactly what you are saying here. perhaps an example would enlighten me Ben.
You'll see that COG/SOG is nowhere to be seen. Neither are Set and Drift. It would be nice if this type of True Wind was always written as True Wind Relative to Boat, but that's a mouthful.
If someone wants to argue that True Wind (RtB) is not really True because it's not necessarily the same direction and speed as the wind actually blowing over the earth, I wouldn't argue.
But sailors have been forever using the term True Wind to mean the wind blowing over their boat if it was stopped in the water, regardless of how it's drifting in current. And it's a very useful metric because it provides a consistent performance base.
If your boat with the #1 set can go 7.8 knots (STW) with the True Wind (RtB) 100 degrees off the starboard the bow at 14 knots, it should be able to perform the same on the port tack, or in the same wind tomorrow.
But that repeatability will not work for you if you correct your apparent wind with COG/SOG, which measures both how your boat is moving through the water and how the water is moving under it. You will get a measure of True Wind Relative to Earth (aka Ground Wind), useful for weather analysis and navigation. But unless the current happens to be perfectly square to the Ground Wind, you're going to appear to point higher into the wind on one tack than the other even if the sails are set perfectly on each.
There are two True Winds, both useful, though confusing!
Posted by: Ben E at October 6, 2009 8:33 PM |Reply
Anybody want to take a crack at explaining current wind or the infamous "lee bow effect" to Tillerman?
Smiling at this whole discussion; we won a regatta this weekend on the Hudson with a 3+ knot current flowing up the course. 20 degree laylines upwind & some of the boats took 15 minutes after setting the spinnaker to get back to the WINDWARD mark!
One of the most fascinating and timeless controversies in our sport is over what effect current has on how we sail and race our boats. Beginning in early 1979, Peter Isler and I filled hours of time debating the effects of current, and it wasn't until mid-1980 that he finally parted my clouds and shook me loose from years of misconceptions and incorrect assumptions.
This is an embarrassment to wake up to: The USSailing calculator I linked to above asks for GPS speed, i.e. SOG, not STW. Goes to show the depth of ambiquity on this subject (and how the eye can be fooled by the brain's presumption). The calculator, mind you, seems to be part of a rudimentary sailing course, and for many boats SOG is more available or more accurate than STW these days.
However, I stand by my assertion that True Wind relative to boat, aka TWA/TWS, is properly calculated using Speed Thru Water, not SOG/COG. Maybe a true expert like Bob Congdon can step in here to verify (or further embarrass me ;-)
Posted by: Ben E at October 7, 2009 8:30 AM |Reply
Has anyone ever experienced the CS4500 interfering with depth transducer signals?
Posted by: AaronH at October 7, 2009 8:52 AM |Reply
Ben wrote:
"However, I stand by my assertion that True Wind relative to boat, aka TWA/TWS, is properly calculated using Speed Thru Water, not SOG/COG. Maybe a true expert like Bob Congdon can step in here to verify (or further embarrass me ;-)"
The "true experts" agree with you Ben (don't you Bob...?!). True Wind (relative to water surface) uses STW. Ground Wind is relative to a fixed geographic point and used for forecasts and routing only - you can't use it for repeating performance metrics etc.
If anyone doubts that they could try sailing in a 10kt Ground Wind (sounds like a nice sail?) with 10kt of tide in the same direction (result: TWS=0, zero Boat Speed [STW]) and then waiting for the tide to turn 180 and doing it again (result: TWS=20kt and plenty of forward motion to get you out of this awful tide I just created...)
Posted by: AlanD at October 7, 2009 1:17 PM |Reply
In between flights with only time to completly agree with Ben & AlanD who both get it.
If Alan is who I think he is we all should pay attention.
Yep, Alan.Ds explanation was smack on, I'm with Bob, Alan & Ben on this, us sailors want True wind on the water (Sailing Wind) not Ground Wind.
Posted by: DavidM at October 8, 2009 8:17 PM |Reply
I have also been using the CS4500--originally as part of Raymarine ST60 system. Last year, I started replacing my st60 instruments with st70s. I also added a st70 speed pod that converts the cs4500 output into NMEA2000. The upgrade went without a hitch.
One additional feature of the st70 displays/pod is that the speed can be calibrated at different speeds. This increases the accuracy greatly--particularly nice on a sail boat.
Posted by: Jeremy Anwyl at October 8, 2009 11:06 PM |Reply
I spoke to Airmar this week as I was interested in replacing my depth/speed/temperature transducer with something ultrasonic, but I only fit NMEA 2000 stuff. Here is what they said:-
"Thank you for contacting AIRMAR Technology Corporation. We are working on a new ultrasonic depth, speed and temperature sensor that will also be NMEA2000. I expect this product to be introduced next year probably in Q2. While preliminary at the moment, the new model is most likely to be called a DST900-CL"
I am going to wait for this.
Posted by: tim shears at October 9, 2009 4:34 PM |Reply
The 4500 is too good. When a sail boat hits a wave, the 4500 shows the results which scares skippers. Needs more damping to avoid the real jumps and drops in speed, even with inst damping on max. All the problems should be solved with the replacement. And no more box. Everything in the core. And anybody who uses Raymarine instruments for any reason and expects accurate wind, speed or heading is dreaming. Approximations yes. Reality no. Anybody replying to the contrary works for Raymarine, or needs new bifocals.
Posted by: Dicko at October 10, 2009 11:46 PM |Reply
The DST900-CL is a great news. On my cat I have a NMEA2000 network and a ST70 with a windpod. Unfortunately the TWA (true wind angle)and TWS (true wind speed) only work with SPEED not with SOG from gps. consequently as time goes the paddlewheel gets messy and SPEED gets inacurate thus the TWA and TWS.
In the past, on my racing boat she was equipped with a transducer like the DST900-EM and worked very well and with great acuracy.
Wait for the DST900-CL
jj
Posted by: jj calypso magic at October 11, 2009 5:28 AM |Reply
Reverse Test: In response to several inquiries on what happens in reverse, I ran a quick test today.
The ST60 Tridata display shows positive numbers in reverse (no surprise, several readers predicted that), however once I reach 0.8 knots in reverse, continued increases in reverse velocity up to 5 knots yielded no higher than a 0.6 to 0.8 knot measurement.
A very interesting discussion with so much information. I have recently installed a Garmin 4012 with a N2K GPS transducer. Soon I must replace the NKE depth/speed kit which is now 19 years old. From the discussion, I think it will be beneficial to wait for the DST900-CL. Thanks so much. T
Posted by: Terence Brace at October 13, 2009 10:25 AM |Reply
Dan Corcoran asked that I post a comment on this article with regard to my use of TWA, TWD and TWS as well as my use of ultrasonic speedos.
I have an NKE HR Pilot and NKE instrumentation installed on my Class 40. This is a recent upgrade to my prior installation of the standard NKE package of instrumentation and pilot. NKE has a top-end package of instrumentation called the "Regatta Processor" and a top end auto-pilot package called the HR Pilot. They leverage the same sensor package, and the HR Pilot package is essentially the same as the Regatta Processor with the addition of a separate Pilot CPU, the pilot ram and rudder sensor, and then additional processing software. The solution was developed by NKE initially for the Vendee Globe sailors, with the instrumentation refined for inshore racing at a Grand Prix level. I could go on for quite some time about the package, but the short story is that it is amazing. The standard NKE package was darn good, and this is nothing short of incredible.
One of the benefits of the package is that it uses sensors and a bus that transmit at 25 hz, with superior accuracy. As such, it makes use of ultrasonic speedos which are a step up from NKE's electro magnetic speedos in both accuracy and speed. I note that Bob C commented on the speedos, so the only thing I can really add is that the NKE solution also makes use of a proprietary GPS antenna with 1 meter accuracy and very, very fast update rate. The software is written to allow for the GPS SOG to substitute for the speedo boat speed should the speedo's produce innacurate data. In fact, in the last Vendee Mich D's speedos were inadvertantly trashed by a solvent used to clean the bottom of the boat prior to the race, and he ended up going around the globe using GPS SOG input only. That seemed to work out for him.
Dan also asked me to comment about the value of TWD, TWS, and TWA. Simply put it, it matters for pilot performance and also for managing the boat's performance. For performance, all of my polars (and sail cross over charts) are laid out for true wind. Having those data values are critical for me to know how I am performing versus my polars, and for understanding which sail and ballast configuration I should have dialed in for the conditions. For the pilot, the true wind mode is critical for maximizing performance when the boat is going up wind or down wind, helping me squeeze maximum speed out of the boat while aslo avoiding crash gybes. This is even more critical in a heavier sea state where the boats motion will end up throwing the apparent wind all over the place. The performance of the HR pilot with regard to its ability to react to and even anticipate boat motion is a quantum leap over the standard NKE pilot, and just does not compare to my experience with a Raymarine pilot. I could always steer better than the Raymarine pilot, in any conditions. The standard NKE pilot could steer as well as I could in many conditions and did a decent job even in the conditions where I was better when hand steering. The HR Pilot steers as well as I can in all conditions, and better than I can when going up wind or deep down wind in difficult, heavy, shifty conditions and it does that because of the quality of the true wind data and its ability to react virtually instantly to the slightest shift or change in conditions.
(Dan - I hope this was what you were looking for)
Posted by: Michael at October 31, 2009 1:27 PM |Reply
Michael races single and double handed on his extraordinary 40 foot racing machine and can be found on other forums commenting on obtaining and using true wind (relative to water).
I have just heard from JGtechnologies that the DST 900 CL will not be available until 2011/12. Has anyone here some influence at Airmar to get them to expedite the unit?
Posted by: Terence Brace at February 11, 2010 7:02 AM |Reply
I made this query to Airmar:
PANBO weblog has mentioned a new depth, speed, and temperature tranducer (N2K) which uses ultra sonic sensing and no paddlewheels. It was referred to as DST900-CL with availability about now. May I ask if this is still a realistic time frame, if so where can I get one.
Thank you,
Terry Brace
Here is their response:
Response (Irene) - 02/19/2010 12:51 PM
Dear Terence,
Thank you for contacting AIRMAR Technology Corporation. We are working on a product like this, but we do not plan to go to production on this until the fall.
If you require any further information, please do not hesitate to contact back.
Sincerely,
Posted by: TJ Brace at March 9, 2010 10:30 AM |Reply
Sorry about that TJ, but I think it was just the commenter "Chris" above who mentioned a shipping date for the new triducer. Which is not say he necessarily misconstrued what Airmar told him. The company does have a habit of announcing overly optimistic shipping dates, when in fact the shots are called by possibly perfectionist engineers ;-)
Anyone had recent experience with the current production Airmar sonic speed xducer? We have a few clients it would be a good fit for, but have stayed away from the product since its early problem days.
Posted by: emsusa at August 8, 2015 11:17 AM |Reply
My CS4500 is from 2011, installed early 2012. I have used it during a sailing sabbatical as well as normal weekend and vacation use before and after that.
It is still working reasonably good and has no fouling problems. I find that it reads grossly incorrect on rare occasions when there is a significant cross-current (not always when there is a cross-current and never when there is no cross-current). Otherwise I'm pretty happy with it. I never had a fouled log ever since I installed it and I had one every weekend with my paddlewheel log before that.
I guess I would buy it again. However, don't expect perfect readings just from using this advanced technology. It requires serious calibration as does any normal log. The main plus is no fouling.
Posted by: Henning at August 9, 2015 4:08 PM |Reply
Thanks Henning, nothing like hearing from the real world. Your review is not so surprising. We were an early adopter of sonic (K-Tech I think it was) for the 1999/2000 Americas Cup but we went back to Signet paddles, which are to this day the choice of every racing boat I know of.
Posted by: emsusa at August 10, 2015 12:40 AM |Reply
I've got an Airmar CS4500 with Nexus NX2 instruments. It reads about 20% over speed and the NX2 has no correction for over-reading logs.
Posted by: Anonymous at October 17, 2015 11:45 PM |Reply
Having a dry bilge, not possible when swapping out paddle wheels, is also a great feature of the CS4500. Having a small water leak somewhere up front I am re-learning what it is to have a wet bilge and fighting mildew in places I cannot reach. I wrote about my mildew fighting tactics, and didn't realize up to this point how much the CS4500 was contributing!
Hi there - I am looking at purchasing the CS4500, primarily b/c my yacht lies in a river on a swing mooring and every time I take her out her current paddlewheel speed sensor has fouled up and I get no speed reading, requiring me to pull it out and clean it. I have a raymarine instrument package (ST60) and an Ray A77 MFD. I need accurate speed for true and apparent wind.
The river /e estuary I am in quite silty and a reasonable layer of slime and mud builds up quite quickly on the hull.
Question I have is whether anyone has any experience with the CS4500 and whether such a layer prevents the operation of the instrument (in which case why would I change it???)
The Ray depth sensor doesn't seem affected by the mud and still produces a signal so I am hoping the CS4500 would as well.
Thoughts?
Posted by: Paul at September 5, 2016 8:41 PM |Reply
I hear rumors (from the Panbo twitter feed no less) about a new Airmar DX900+ that sounds pretty interesting. We'll see a main site post on this soon I hope?
Yes, indeed, but right now I don't know anything more than what the DAME award site says:
"DX900+ MultiLog -- Airmar Technology
Industry’s first Bluetooth®-enabled, multifunctional sensor Available outputs include: Dual axis, electromagnetic speed sensor, integrated water depth, fast response temperature sensor, and three-axis accelerometer all with no moving parts. In addition, the sensor measures and outputs leeway."
I did ask Airmar for more information but they just politely told me that they are excited about introducing the DX900+ at METS.
Posted by: Ben E in reply to JWS at October 24, 2016 7:17 PM |Reply
I saw the Panbo Facebook page comment on the DX900 and sent an email to Gemeco to see when it might be available. The reply was that it's not even in production, which means to me it may never be. DAME should not give out awards for products that can't be bought and are still concepts.
Posted by: Richard C at October 25, 2016 11:47 AM |Reply
A speed sensor that reads velocity in two axis so as to report leeway, the almost unknowable component of navigating a sailboat, ... that's a really big deal. I believe it was announced that this was being tested on several sailboats this year (I would have loved to test it).
The CS4500 is less accurate than a clean paddlewheel as evidence the output from the CS4500 is a bit noisy in some conditions, yet wonderful more accurate than even a slightly fouled paddlewheel. Would like to know if the DX900 improves upon the CS4500 in straight up accuracy and have high hopes the major players will accept leeway measurements into their products rather than just plugging in an estimate.
Dan, I know that a few years after you posted this Panbo entry I called Airmar and asked if they planned on making a CS4500 for NMEA 2000 and their answer was yes, but it would be awhile. I was thinking in terms of months but Airmar was thinking years.
If anyone should be testing a DX900 it should be you. I know you would give it a thorough evaluation and report back in great detail. I’m not racing my heavy cruising boat, however, I have a background crewing aboard race boats out of Huntington and Oyster Bay and appreciate the accuracy of boat speed vs GPS speed not to mention the holy grail of boat data - Leeway. Hope Airmar sends you one to test. We would all benefit greatly.
Posted by: Richard C at October 26, 2016 6:56 AM |Reply
I wrote above that my CS4500 reads grossly incorrect when there is a cross-current. I think I may change that to "in silty water" (the two often go hand in hand).
Based on that, I wouldn't recommend it in a muddy river - as Paul asks above.
On the other hand, mine has held up a good number of years now and on this summer's cruise, as soon as we left the Elbe river and entered the clear Baltic, it performed accurately all the time. Until we returned to the Elbe at the end of the cruise, that is.
By "grossly incorrect" I mean that when going a consistent 6.5 knots SOG, the CS4500 readout will swing like a sine wave between 0.1 knots and 9.5 knots about one cycle per 30 seconds, completely unrelated to the actual speed of the boat.
And I am done waiting for any product from Airmar to arrive any day now for at least this lifetime.
Posted by: Henning at November 2, 2016 1:31 PM |Reply
My experience with noisy was more in the +/-0.2 knot range most of the time and sometimes more, where the value would jump around a bit so you couldn't tell right away if your accelerating or decelerating in response to sailboat trim.
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at October 5, 2009 9:53 AM 
With the improvement in the accuracy of GPS, I did a comparison and found the GPS determination of speed to be more accurate. The paddle wheel and ultrasound sensors are the vector sum of current and SOG while the GPS is only SOG. I'm not sure what role the through hull sensors have with the adoption of GPS.
Even the hand held GPS units are remarkably accurate. Other thoughts from the readership?