Re: [PSUBS-MAILIST] speedo

[Cliff Redus <cliffordredus@sbcglobal.net>]

David

 

On the R300, I use a pitot tube with a differential pressure transmitter.  In my PLC I programmed an equation that correlates differential pressure and speed.  While this has worked OK, it is not as accurate as I would like at low speeds.  If I had to do it again, I would use a paddle wheel that gives a pulse count that is proportional to boat speed.  You can get these as replacement parts for jet skis.  The results should be more linear than for a pitot tube.

 

 

Cliff

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From: "ShellyDalg@aol.com" <ShellyDalg@aol.com>
To: personal_submersibles@psubs.org
Sent: Sun, October 31, 2010 7:28:52 AM
Subject: Re: [PSUBS-MAILIST] speedo

In a message dated 10/31/2010 5:11:51 A.M. Eastern Daylight Time, dbartsch2236@hotmail.com writes:

Can anyone describe how a speedo speed indicator system works

Hi David. I'm not sure what a "speedo" refers to here but for surface boats that measure the speed in knots, there's usually a small paddle wheel inset into the hull that spins as the water passes over it.

Most I've seen ( on sail boats ) use magnetics to send the signal through the hull to a tachometer like device

that in turn sends the speed signal to the little gage on the dash.

The paddle wheel is VERY small, like 1/2 inch diameter.

Frank D.