NKE Ultrasonic Log

Doppler sonar logs have been around for a long time but have never been successful in the leisure market for some reason despite being theoretically very accurate. I used to sell commercial marine ones in the 70s and they were very accurate. NASA were the first to sell leisure ones based on a doppler pipe flow sensor. They seem to have problems with them because they stopped selling them. I see from the Airmar data sheet they are also offering EM logs. We used them in submarines and they were pretty accurate but needed many measured mile runs to calibrate them
 
Airmar have made the ultrasonic CS4500 log for many years. I don't know why more people don't use them. I've had one for six years and I'm happy with it. It seems more accurate than paddle logs and is vastly less affected by fouling. It does get confused by murky water sometimes, but this is not a big problem. Small faff to install in an N2K network because it outputs the old pulse signal, which has to be converted to 0183 with an Actisense box, which has to be converted again (in my case, via the 0183 input on my Zeus plotter), and it's relatively expensive, but for me it's been well worth it.
 
Dockhead said:
Airmar have made the ultrasonic CS4500 log for many years. I don't know why more people don't use them. I've had one for six years and I'm happy with it. It seems more accurate than paddle logs and is vastly less affected by fouling. It does get confused by murky water sometimes, but this is not a big problem. Small faff to install in an N2K network because it outputs the old pulse signal, which has to be converted to 0183 with an Actisense box, which has to be converted again (in my case, via the 0183 input on my Zeus plotter), and it's relatively expensive, but for me it's been well worth it.
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Quick question is it water lock or bottom lock or can it be switched between the two.
 
I think the technology has moved on. NASA have just brought out one as well for much less cost; I am in the process of fitting one. Good riddance to paddle wheel logs, which either under-read or don't read at all.
 
Boathook said:
We had a Seafarer doppler log back in the 70's. Had to keep the screws clean so that it worked.
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We also had the Seafarer, but as far as I remember it was not Doppler but 'electronic'. There were Doppler logs around at the time but the B&G and Seafarer were different. I think that the Doppler logs were effectively echo sounder but the electronic ones created an electric, or do I mean electromagnetic, field and measured its distortion, hence the metal screws, though I don't remember having a problem with them fouling.
 
yerffoeg said:
I think the technology has moved on. NASA have just brought out one as well for much less cost; I am in the process of fitting one. Good riddance to paddle wheel logs, which either under-read or don't read at all.
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All I can find is an EM log a very different beast. In the old days they needed many measured mile runs to calibrate them
 
Apologies. Yes the new NASA instrument is an EM log. The calibration procedure mentioned in the instructions appear simple enough.

Yes, I will report back at the end of the season.
 
I don't see why the calibration should be any different to any other, or any more difficult. In ye olden days we used to use measured half miles to calibrate with, or sometimes by comparison with a Walker log, which was easier. I don't suppose that electronic logs are significantly more linear than paddle wheels, though they may be. I have always taken a flexible approach to calibration, accepting that you are never going to get it exactly right for all conditions. My normal practice is to set it approximately right by some means, maybe by GPS comparison in still water, and then tweak it to what I want, which is to over-read by 0.1-0.2kn at about 6.5kn in deep water. I mention deep water because my boat is slowed by shallow water <5m but the log over-reads.
 
yerffoeg said:
I think the technology has moved on. NASA have just brought out one as well for much less cost; I am in the process of fitting one. Good riddance to paddle wheel logs, which either under-read or don't read at all.
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Where did you get it? Quick look on google no one had any in stock yet. Ta, going for one for sure at that price :cool:

Should fit down an ST60 tube?
 
johnalison said:
I don't see why the calibration should be any different to any other, or any more difficult. In ye olden days we used to use measured half miles to calibrate with, or sometimes by comparison with a Walker log, which was easier. I don't suppose that electronic logs are significantly more linear than paddle wheels, though they may be. I have always taken a flexible approach to calibration, accepting that you are never going to get it exactly right for all conditions. My normal practice is to set it approximately right by some means, maybe by GPS comparison in still water, and then tweak it to what I want, which is to over-read by 0.1-0.2kn at about 6.5kn in deep water. I mention deep water because my boat is slowed by shallow water <5m but the log over-reads.
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Certainly the ones we had on submarines were not linear hence the multiple runs and we had two of them. I seem to remember the calibration being applied using a cardboard cam. Of course as we often ran for many hours on DR using AR plotting tables we did need as accurte a log as we could get, especially as the log also was a key input to the fire control system
 
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