Hi
I have a NKE ultrasonic sensor since one season. Until now, I find it reliable and linear.

rgds

I used a CS4500 in 2014 to 2017 with great accuracy until it started to behave strange and soon after stopped working completely.
I went back to the Airmar standard paddlewheel although I miss the accuracy of the CS4500.
Btw. the power/signal interface box of the CS4500 did not work out of the box with my Tack-Tick. It needed some modifications.

Airmar has a new ultrasonic unit now, UST800/850 where they appear to have moved some of the signal processing out of the sensor into an interface box. Maybe this has improved reliability?
Anyone with experience of this new unit?

Howdy --  I tried to get more info about ultrasonic speedos from Airmar.  The back and forth follows.  To their credit, they did respond, but not substantively in my opinion.
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Original Help Ticket to Airmar:
Date submitted: 8/13/23
Reference number: 1831161113
Issue: Ultrasonic Speedos
Issue description: My CS4500 has quit working. I see many, many complaints about this product in multiple forums. Is your new product UST800/850 any more reliable?
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On Mon, Aug 14, 2023 at 11:02 AM support < support@airmar.com> wrote:
Good day, We don't see any reason you want get great service with the UST800/UST850. Unfortunately with any electronics they can fail, but I will say that's far and few between.
Best regards,
The AIRMAR Product Support Team
www.airmar.com
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Date: Monday, August 14, 2023, 6:38:25 PM -0400
Subject: Re: Ultrasonic Speedos
To: support <support@airmar.com>
Thanks for the reply, but, I have a CS4500 that worked for about a year, then failed.  It appears that many, many people who bought the CS4500 have had similar experiences.  Is the UST800/UST850 more reliable than the CS4500?  If so, what have you done to improve the reliability?
Regards,
Mark 
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 The CS4500 failure rate while inside the two-year warranty period, has always been well under 1%.  The UST800/850 rate will fall into the same range, well under 1%.  As with any product, it is very rare for someone who has a perfectly operating product, to go onto the internet and make repeated posts stating how well their device works.  The very small percentage of failures tend to get nearly all the attention, which is then perceived as a higher failure rate than what is actually occurring.
 
Best regards,
The AIRMAR Product Support Team
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Date: Tuesday, August 15, 2023, 11:08:46 AM -0400
Subject: Re: Re: Ultrasonic Speedos
To: support <support@airmar.com>

I appreciate the reply and those statistics.  However, the experiences of the competitive yacht racing community seem to differ significantly from your statistics.  Please let me elaborate:

The accurate measurement of boat-speed (through the water) is a key parameter in sailboat racing.  It is used to develop accurate performance polars and to monitor and optimize sail trim.   At the upper end of the sport the crews and management of these boats are paid professionals.  These guys will leave no stone unturned in coming up with reliable performance data.  Their standard for boat-speed measurement has been the old paddle-wheel, even though it must be removed very, very frequently for cleaning to ensure accuracy-- even then, one is never sure that it is as clean as it was on the last calibration run.  BTW, good calibrations take hours of effort and selection of a day with little wind and current-- takes a lot of time, even then it is difficult to calibrate the upper speed end of these inherently nonlinear devices.   So, the advent of a technology that has no moving parts to become fouled, and is more inherently linear should be of great interest to competitive yacht racers.  Yet, the reality is that the vast majority of competitive racing programs rely upon the paddle-wheel because your ultrasonic transducer technology has had far higher failure rates than the paddle-wheel.   Those are the facts on the water, or, at least, this is the perception.  No one at the higher end of the sport, to my knowledge, uses ultrasonic transducers.  All of the experts (competitive navigators) advise the use of paddle-wheels, this despite all of the hassles and inaccuracies in using paddle-wheels.

I'd be interested to know whether your failure rate statistics for the paddle-wheel are significantly lower than your rates for the ultrasonic transducers. 

Also, if you are so certain of the reliability of your ultrasonic transducers, why have you invested in a new paddle-wheel technology which you recently introduced?

I am very interested in using ultrasonic transducers on my boats, but having been burned once by the failure of your CS4500 I will need more convincing before trying one of your ultrasonic transducers again.  Convince me.  Show me the data you have on failure rates for the new USTs. 

Please advise, Mark
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Thank you for explaining what your observations have been.  The questions you asked, we are unable to provide an answer for.  We are no different than any other company, we would never share internal information regarding product development, specific means and frequency of a products failure, etc..  We are very confident in our products and know that any failure rate is under the industry average.  Thank you for your interest in our products.
Best regards,
The AIRMAR Product Support Team