On Wed, 26 Jan 2005 01:54:48 +0000, bing2005
wrote:

Can anyone please tell me how did the speed transducer of SPEED2100
measure the speed of the boat?
I try to design my own display unit for this speed tranduscer. However,
i dont know the operation of the speed transducer, such as how i
calculate and measure the speed through the paddle wheel of the
transducer. When the paddle wheel is moving, how i going to know the
speed of the boat?
If anyone know, please tell me.
Thanks a lot!!!


As others have said, the wheel sends pulses on each rotation.

You have to come up with a conversion rate for how
many pulses relate to what distance. Then you must
calculate how that distance over time relates to speed.
You could measure distance with a GPS or by driving the boat
over a measured course and recording the pulse count
over the distance. You will probably have to gather this
data for a great many boat speeds, since it may vary
with speed and sensor location on your boat. You will
have to make two-way runs and average them to compensate
for any current in the water where you make these tests.

If you do this carefully, you should end up with a
speedometer/odometer that is more accurate than the
one-size-fits-all that you get when buying a ready-
made speedometer.

There just ISN'T any way to calculate this from things
like paddlewheel diameter or blade size (which is what
I suspect you were hoping for.) The original manufacturer
had to do something like this to design the software
in the display unit. You will have to do it yourself
if you want to design one of your own.