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Any good options for NMEA 2000 Depth/Speed Transducers?


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A few years ago I bought about $8k of Garmin gear to gut the aging B&G stuff on my J/35. I am generally pleased with it, but I did run into an issue about a year after installation - the Depth/Speed transducer started to periodically cut out. I checked and cleaned all of the connections to no avail. Contacted Garmin for help - this was an utter waste of time! Garmin uses a company called Airmar to make these things and the two passed me back and forth for hours asking the same questions about serial numbers, receipts and stuff... I dug out all of the information they wanted and in the end neither would honor the warranty. Airmar said Garmin is responsible because it came as part of a Garmin kit. Garmin said that I was 2 months over my warranty even though I originally called about diagnosing the problem months earlier and got the runaround....

Anyway - the new part is available through Amazon for $255 https://www.amazon.com/Garmin-AIRMAR-DST800-Sensor-thru-hull/dp/B001DF9Q6U 

But reading the reviews, users report that these things commonly last only 2-3 years, which sounds ridiculous to me! My B&G setup had a lot wrong with it, but the transducers were at least 20 years old and that was one of the few things that weren't broken. 

Pertinent question: I am pretty sure that the Garmin stuff runs on a NMEA 2000 back end. Is there some generic depth/speed transducer that I can buy that will work with the main brain and not require regular replacement?

Thanks in advance!

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Airmar is the generic source for most transducers for most brands of instruments. $225 is about right for a new combo transducer.

It's worth noting that the speedo in that unit is not very good at low speeds, but with your Garmin system I believe you're stuck with no analog speedo capability.

 

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Pretty much useless with most instrumentation systems as they can't display leeway, they compute it from boat speed heading and sog and cog. You need expedition or adrena and an instrumentation system that supports user variables.

And last I knew it was 0183 only.

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6 hours ago, Moonduster said:

..., they compute it from boat speed heading and sog and cog.  ...

I immediately thought you need to measure the actual direction of the flow (relative to the boat CL) so I googled it to see if I was stupid. Found a thread on it in Gear Anarchy, and it appears I am not stupid, at least not in this case. :)

 

The thread seems to have stalled since November.

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I'm well aware of that sensor. My post was trying to say that it can't be integrated into most instrumentation systems because there's no leeway standard for in NMEA2000 or NMEA0183 and most instrument systems compute it themselves. The only way to get it through most systems is as a user variable extracted from the raw data by Expedition or Adrena.

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Garmin actually sells their own analog speed transducer bundled with an analog-NMEA 2000 converter. The transducer is the old Nexus 43 mm transducer which in my experience is better than the Airmair transducer (more linear over speed) and almost as good as a Signet blue-cap. Need a separate depth transducer though. 

https://buy.garmin.com/en-US/US/p/pn/010-04284-00

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Guys - I do not really care about measuring leeway (I can see it on my plotter quite well and I do get GPS speed/heading). What I am searching for is something that will give me a depth reading (most importantly) and boat speed over water (two units would be fine) so long as I don't have to change them out every 2 years. 

What I am hearing now is that this is not an option??

Yes - in my experience, the paddle wheel on the airmar sensor sometimes take 1-1.5kn of water going over it to start moving. But that is generally not a huge problem. The biggest issue for me is losing our depth reading when doing close in-shore zig-zags on a competitive race. Here in Puget Sound dealing with currents is a major thing in sailboat racing.

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I would recommend using "dumb" transducers and interfacing them with a box that gets them onto the NMEA 2000 network.  I use a Raymarine iTC5 for doing this on my boat, but I think you can get a similar box from Navico or Garmin.

There is no good reason to integrate the expensive electronics into the cheap transducer, it makes more sense to have a single expensive box (~$200) that gets all of your transducers onto the network and handles calibration of them.

 

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I'd honestly suggest you stay miles away from this tri-sensor.

We had one installed in our new yacht 6 years ago as part of a Raymarine package and it was replaced 4 times under warranty (with us paying haulage for 2 of those) before we demanded a solution from Raymarine which was only resolved after getting our fair trading people involved. Issue on all 4 occasion was the flap that prevents water gushing in when you change the transducer falls out and you get firehosed every time you remove it after sailing.

We now have a standard Depth and seperate Speed/Temp which are connected to the network with an iTC5 box, its been in the boat for 2 years now with no issues. Yes it did involve another hole in the boat but it works every time.

FYI I know of 4 other local yachts with similar issues to ours in the same time frame.

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OK - this iTC5 seems like a good idea! However, how do I know which transducers will work with this box? It says "analog" but I assume there is more to it than that!

Luckily, my boat has two through-hulls at the bow, which is how the B&G stuff worked - one was speed, the other depth/temp. Im starting to think that you guys are right - packing all 3 functions into one thing doesnt seem like a good idea. Any pointers on which transducers to get? (BTW, I could care less about water temp).

 

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The iTC5 is calibrated by a Raymarine i70 display (or newer MFDs I think).  For speed it can calibrate any reasonable pulse length, for depth it just needs a 200khz transducer.  If you have Garmin instruments I would look to see if they have a iTC5-like device.

I'm using Raymarine (really made by Airmar) transducers for wind, depth, speed, but if I were buying new and had the boat hauled out I would get the more accurate signet speed.

Depth transducers rarely die and so there is rarely a reason to upgrade them.  

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I've been told that depth sensors are sensitive to low battery voltage levels.  No clue what your situation is, but something to keep in mind when your depth readings aren't reliable.  Also - Puget Sound is notorious for thermoclines.

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On 5/7/2019 at 7:23 AM, Pelle said:

Garmin actually sells their own analog speed transducer bundled with an analog-NMEA 2000 converter. The transducer is the old Nexus 43 mm transducer which in my experience is better than the Airmair transducer (more linear over speed) and almost as good as a Signet blue-cap. Need a separate depth transducer though. 

https://buy.garmin.com/en-US/US/p/pn/010-04284-00

This works well and provides N2K data at a 5Hz rate.  It needs a Garmin device to calibrate it. I confirmed that when I did an actual install and could not access the cal features via a B&G Triton 2 display without a Garmin display device (Garmin chart plotters on N2K network work).  Once the Garmin device calibrated it, the B&G device could be used ofr further calibration.  There is an old thread that has a good discussion about this.

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  • 3 weeks later...

I have a Raymarine ITC-5 and Raymarine i70s Display unit.  It came with the Airmar DST800 transducer but my 1986 Cal  28 has Signet sensors.  The Depth sensor displays just fine using the ITC-5 but not the old analog boat speed sensor.  I just got a blue Signet Hall effect sensor that puts out a square wave at a frequency of about 10 hz/knot which could be calibrated in the i70s.  But so far I only get it to read 0.0 when I spin the paddle.  The problem, I gather, is that I need to convert the analog blue Signet sensor output to NMEA200 to imitate the DST800 but that's what I thought the ITC-5 was for!  I've been reading older posts from WHK and Alex W and get the impression WHK figured this out, at least using Garmin devices (G43/GS10).  But the Garmin GS10 manual says it doesn't work with Signet.

Any suggestions are greatly appreciated.  I have 30 days to give up, send the blue Signet sensor back, and stick with the barely readable old Signet  Smartpak display for boat speed.

 

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If you don't mind 2 holes separate speed and depth transducers are the way to go. We've moved to recommending the GST43 becasue it's easier to get hold of than the Signet.

The DST800 is fine but compromised. For some reason, the signal rate of the n2k version seems particularly compromised (0.5Hz??)

According to the manual, the DX900 is native 0183 for speed and temp but needs the n2k interface box for depth. We've not been in a hurry to integrate it because of that (would be nice though)

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To explain my issue a little more:  My boat has two holes and separate Signet speed and depth transducers.  I do not want to haul the boat out and enlarge one of the holes to use the Airmar DST800 Triducer that came with my Raymarine set up.  I installed Raymarine for the anemometer and for compatibility with my old Raetheon autohelm.  The Signet depth sensor works perfectly with the Raymarine ITC-5 and i70S display.  But the original Red Signet speed sensor does not.  I just bought the Signet Blue top sensor since it puts out a square wave whose frequency is proportional to boat speed, like the DST800, but so far connecting to the ITC-5 doesn't display boat speed, just 0.0.  I'm wondering if anyone has made this work and if I need some other electronic device to interface between the Signet Blue speed sensor and the ITC-5?  The ITC-5 is supposed to convert analogue signals to NMEA for the display.  Raymarine says only the Airmar sensors work and those have built-in circuitry to output NMEA.  I have had no problem communicating with Signet and they would be very interested to know if their sensors can be made to work with my latest Raymarine electronics.

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9 hours ago, Moonduster said:

Signet hard to get a hold of? Trouble using a telephone and credit card? Perhaps you don't know your shipping address?

Look here. Part number is 1-2200.200. Price is $189.

 

I should of said, outside of the US.

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8 hours ago, Eyewindsurf said:

I just bought the Signet Blue top sensor since it puts out a square wave whose frequency is proportional to boat speed, like the DST800, but so far connecting to the ITC-5 doesn't display boat speed, just 0.0.  I'm wondering if anyone has made this work and if I need some other electronic device to interface between the Signet Blue speed sensor and the ITC-5? 

With the d10 we connect the Bluecap, GST43 and analogue Airmar transducers in through the same input circuit. All good.

We've noticed the signet has a wider practical operating range for voltage and current, so in theory, it should work where ever an airmar works (I wouldn't assume the opposite).

One thing, they all put out different frequency pulses. So an interface set-up for an Airmar (different Airmars put out different frequencies too) will read fast if you connect a signet to it. Nothing a single point calibration can't fix but worth being aware of.

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Thank you rgeek.  Are you saying I need a d10 to connect between the Signet Bluecap and my Raymarine ITC-5?  What's a d10?  I know I'll have to calibrate the Signet down since the Signet does 8 or 10 khz/knot and the Airmair 5.6 khz/knot but that should be easily accomplished by the i70s display.  I plan to fiddle with it more in the next few days.

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The d10 is an all in one instrument with an analogue speed input. Not really helpful for what you're trying to achieve here. I'm just saying all those analogue transducers work with it in the same way.

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On May 7-8 AlexW posted that he has a Raymarine iTC-5 converter- as do I - and that he recommended a "dumb" transducer, specifically the very accurate Signet.  I just got a Signet Blue  speed transducer.  Can anyone tell me that it does indeed work with the iTC-5 to display and calibrate on the Raymarine i70s?   I'm still trying and will let everyone know if it works.

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8 hours ago, silent bob said:

What is the Smart Repeater?

The d10 has three display modes.

 

Smart repeater display mode for larger boats.

It gives you a 4-page repeater with a choice of what to display on the top and middle digits. The graphics area is used for labels. All the d10s functionality is running in the background, but it's controlled from the a10 phone APP rather than with the d10s buttons. The display size on the d10 means it's good for anything from 20-60ft.

 

Regatta mode is optimised for smaller boats.

This includes the following preconfigured pages with button function that allows everything to be controlled from the d10:

- Prestart page: timer and distance to line

- Performance: boatspeed, heading/shift, heel angle

- Depth-tide: boatspeed, heading, depth or the difference between HDT/COG and STW/SOG

- Nav: boatspeed, turn to mark, distance to mark

- Wind: repeater for apparent and true wind

Sports mode is optimised for classes that want to limit the functionality available, such as the SB20, or people who want to simplify the d10s function. It's the same as regatta mode but removed the nav and wind pages.

 

The next version of firmware (v1.5) is due at the end of June. This is the first time I've put any info out on it (including to our distros/dealers) but hey...

v1.5 has a number of tweeks to improve things for boats with 2x d10s or that want to use the smart repeater mode to customise the display.

- The prestart page is made available in smart repeater mode, with auto switch back to the smart repeater 10 seconds after the start.

- The wind page has been revamped to display boatspeed, true or apparent wind angle, heel angle or wind speed.

- The nav page has an option to display heading instead of boat speed

Taken together the last 2 mean you can set the top d10 for the trimmers (boatspeed, wind angle, heel angle or wind speed) and the bottom d10 for tacktics/nav (heading, turn to mark, distance to mark)

... displaying the splits rather than turn on the nav page is on the list for v1.6

 

 

 

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Success!  My Signet blue speed transducers displays just fine now on my Raymarine i70s display unit using the iTC5 analogue to NMEA converter.  The problem was a lack of power to the transducer due to a wiring error on my part.   It is also necessary to connect a $20 temperature sensor (or just a resistor) to the iTC5 as well, and to calibrate the speed display in the i70s.  This is clearly a much better solution than using the Airmar DST800  smart triducer which also requires a larger hole through the hull.  I hope this post is helpful to other sailors of older boats who wish to upgrade to current NMEA electronics while still keeping their analog "dumb" transducers.

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Well, maybe my success isn't quite what I thought.  It turns out the Signet Blue speed transducer puts out a nominal 13.6 hz/knot vs the Airmar DST800 that uses 5.55 hz/knot. I thought I could calibrate for the difference, but when I tried to calibrate the speed display in my Raymarine i70s, the lowest calibration factor available is 50%.   To emulate the Airmar, I need a 41% reduction (5.55 divided by 13.6).  I compared the readings I was getting with the 50% calibration factor to my GPS speed over ground readings and indeed the paddlewheel system read roughly 25% too high.  Old threads on this site include some discussion of using an arduino to reduce frequency.  The saga continues.

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  • 2 months later...

Looks like my thread got a bit hijacked here, but good info! In the meantime my DST800 setup is almost dead (showing no readings at all) about 90% of the time now. 

Based on what I read, I just ordered the Garmin GST-43 bundle and this will give me a speed reading. 

I also looked on Garmin's website and bought a separate GDT-43 depth reading unit. 

Total cost: $430! Ouch! Will report on their performance after install.

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  • 6 months later...

Nice to hear from you Artey.  You probably read my earlier posts.  Since then I've just been using the displayed boat speed reading using the maximum calibration available on my Raymarine i70s display which is 50%.  I use the reading to see if I'm speeding up or slowing down when I trim the sails but  I know it's still reading a bit high.  I use my old Garmin GPS to get a better idea of S.O.G.  That measurement is always less than the displayed boat speed but closer than I expected.  And the conversion doesn't seem to be linear.  Per my earlier posts, I do think I need to decrease my Signet blue output by 41% instead of 50%.  To do that, I bought a cheap breadboard kit and some D flip flop chips.  A friend showed me how to wire the chip so that it cuts the frequency of an input square wave signal in half.  So far, this simple circuit is noisy and not quite working.  If I do make it work, then I'll have a 50%  reduction by hardware and can calibrate down from there in the i70s display.  I'll post again if it ever works.  I plan to haul the boat for bottom painting next month and am considering getting the hole enlarged so I can use the Airmar DST sensor that came with the whole kit.  I'll probably just stick with the Signet blue top until the following haul out in about 3 years.

In the meantime, I'm more preoccupied with a low tech problem:  My engine coolant doesn't seem to be circulating enough (or at all) through my water heater.  It's cold by the time it gets there.

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3 hours ago, Eyewindsurf said:

Nice to hear from you Artey.  You probably read my earlier posts.  Since then I've just been using the displayed boat speed reading using the maximum calibration available on my Raymarine i70s display which is 50%.  I use the reading to see if I'm speeding up or slowing down when I trim the sails but  I know it's still reading a bit high.  I use my old Garmin GPS to get a better idea of S.O.G.  That measurement is always less than the displayed boat speed but closer than I expected.  And the conversion doesn't seem to be linear.  Per my earlier posts, I do think I need to decrease my Signet blue output by 41% instead of 50%.  To do that, I bought a cheap breadboard kit and some D flip flop chips.  A friend showed me how to wire the chip so that it cuts the frequency of an input square wave signal in half.  So far, this simple circuit is noisy and not quite working.  If I do make it work, then I'll have a 50%  reduction by hardware and can calibrate down from there in the i70s display.  I'll post again if it ever works.  I plan to haul the boat for bottom painting next month and am considering getting the hole enlarged so I can use the Airmar DST sensor that came with the whole kit.  I'll probably just stick with the Signet blue top until the following haul out in about 3 years.

In the meantime, I'm more preoccupied with a low tech problem:  My engine coolant doesn't seem to be circulating enough (or at all) through my water heater.  It's cold by the time it gets there.

engine thermo stuck open assuming it did work before?

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9 hours ago, Eyewindsurf said:

Nice to hear from you Artey.  You probably read my earlier posts.  Since then I've just been using the displayed boat speed reading using the maximum calibration available on my Raymarine i70s display which is 50%.  I use the reading to see if I'm speeding up or slowing down when I trim the sails but  I know it's still reading a bit high.  I use my old Garmin GPS to get a better idea of S.O.G.  That measurement is always less than the displayed boat speed but closer than I expected.  And the conversion doesn't seem to be linear.  Per my earlier posts, I do think I need to decrease my Signet blue output by 41% instead of 50%.  To do that, I bought a cheap breadboard kit and some D flip flop chips.  A friend showed me how to wire the chip so that it cuts the frequency of an input square wave signal in half.  So far, this simple circuit is noisy and not quite working.  If I do make it work, then I'll have a 50%  reduction by hardware and can calibrate down from there in the i70s display.  I'll post again if it ever works.  I plan to haul the boat for bottom painting next month and am considering getting the hole enlarged so I can use the Airmar DST sensor that came with the whole kit.  I'll probably just stick with the Signet blue top until the following haul out in about 3 years.

In the meantime, I'm more preoccupied with a low tech problem:  My engine coolant doesn't seem to be circulating enough (or at all) through my water heater.  It's cold by the time it gets there.

Thanks for the additional info Eyewind. Was hoping to make this work mainly to avoid having to do what you explain and enlarge or even worse, shrink the holes. I wasn't sure what the diameter of the signet holes were at the thread side. I'm extremely new to boating and didn't want to remove from the hole only to find that it was larger than the Airmar DSTs. I may bite the bullet and end up with one despite the reports of the unreliability of triducers. Then I can patch the separate depth thru hull at least - yay one less hole to worry about, but booo more fiberglassing :(

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