Originally Posted by colemj
We haven't experienced any problems with our Airmar N2K paddlewheel sensor and it remains quite accurate. The thruhull for it contains a valve which shuts off the majority of the water flow when the transducer is removed. After a passage, we simply pull the transducer and put in the blank plug
. Takes 10 seconds and no mess. Reverse procedure when getting underway again.
No growth and accurate readings.
I think that's the same transducer 99% of cruisers everwhere use, AFAIK. I have had trouble getting mine out so I usually wait until a liftout -- I lift
and scrub every 2 months or so in the summer. If I had mastered getting the thing out so that I could keep it out when I'm off the boat I would of course have had better results with it.
But paddlewheel transducers are inherently inaccurate for different reasons -- for one thing, they measure the speed of the boundary layer (the ultrasonic transducers measure particles going by some distance away -- beyond the boundary layer), secondly they are very sensitive to any kind of fouling and read differently day by day as you cruise
. Lastly, they are very inaccurate at low speeds.
I think it's not just a caprice that I want really accurate STW data. This data is so important for understanding so many things going on while you're sailing -- sailing performance, true wind
, and now, with my new Zeus system, drift and set calculated dynamically.
So I am gladly investing some money
My last question is whether the unit can be conveniently calibrated if I hook it up through a DT800 smart depth transducer. I will call Airmar tech support when it's morning there.
Other options I've discovered so far are:
1. Hook it up through a Raymarine
ST60+ dedicated log or ST60+ tridata, then bridge to the N2K network with a Seatalk
to N2K adapter or Seatalk
to NMEA0183 adapter via one of the Zeuses. Shame I just sold my old ST60 log, which could have been used for this purpose; albeit I would have lost
a hole for an instrument on the scuttle.
2. Hook it up through a Raymarine
ST50i tridata display. This will also connect directly to my old depth transducer, and will bridge both that and the ultrasonic speed transducer directly to N2K. I like this.
3. Hook it up through an Actisense DST2 module, then pipe the resulting NMEA0183 data to one of my Zeuses, which will bridge it onto the N2K network. This will also allow me to save some money
by using the old depth transducer.
4. Hook it up through one of those very cool Raymarine ITC-5 transducer adapters, which will allow me to use my old depth transducer as well.
So I have five apparently viable options. The two I think I like best are (a) using the Airmar DT800 to bridge the speed data; and (b) using the Ray ST50i Tridata. I think the Tridata will even bridge my backup wind
data (I am leaving my old wind transducer at the masthead), so I will have both streams of wind data on the network. Cool! Cost-wise there's not much to choose between these variants -- cheapest is probably the surprisingly economical ITC-5.